the chondroeranium of calotes versicolor (baud.) with, a...
TRANSCRIPT
The Chondroeranium of Calotes versicolor(Baud.) with, a Description, of the Osteocranium
of a just-hatched YoungBy
L. S. Eamaswami(Department of Zoology, University of Mysore,
Intermediate College, Mysore)
With 16 Test-figures
CONTENTS PAGE
1. INTRODUCTION 237
2. MATERIAL AND METHODS 238
3. OBSERVATIONS 238
I. Chondroeranium of Calotes versicolor (Daud.)(a) Embryo, head-length 3'6 mm.(6) Embryo, head-length 6'0 mm.(c) Embryo, head-length 7'0 mm.(d) Embryo, head-length 8'0 mm.
II. Osteocranium of a just-hatehed young of Calotea veraicolor(Daud.), head-length 8-0 mm.
INTRODUCTION
THE chondroeranium of a number of lizards has beendescribed, viz. Lacerta (Leydig, 1872; Parker, 1880;Gaupp, 1900, 1906; de Beer, 1930); Ascalabotes (Sewerfc-zoff, 1900); Hemidactylus , P la tydac ty lus (Versluys,1903); Anguis (Zimmermann, 1913); Eumeces (Eice,1920); Lygosoma (Pearson, 1921); P la tydac ty lus(Hafferl, 1921); Lygodactylus , Pachydactylus, andAgama (Brock, 1932); Ablepharus (Haas, 1935). In thedescriptions of the adult skull of Chalcides (Haas,1936) and Acontias (de Villiers, 1939) persistence ofchondrocranial cartilages in various regions is also noticed.Boulenger (1890) gives figures of lateral, dorsal, and ventralaspects of the adult skull of Calotes juba tus (Dum andBibr.) which are also reproduced in the latest edition of "Sauria".a "Fauna of British India" (Smith, 1936). The columella
2S8 L. S. EAMASWAMI
auris has been-studiedinLacerta (Hoffmann, 1889; Versluys,1898, 1903; Cords, 1909; Dombrowsky, 1918, 1924), and theadult hyoid apparatus of Oalotes ve r s i co lo r is describedby Gnanamuthu (1937) and Narayanaswamy Iyer (1943).
I propose to describe in detail the fully formed chondro-cranium of Calotes ve r s i co lo r (Baud.) while makingreferences to important points in three earlier stages, and aswell the osteocranium of a just-hatched form. The adult skull isdescribed by Narayanaswamy Iyer (1943).
MATERIAL AND METHODS
The following are the stages of Calo tes v e r s i c o l o r(Baud.) studied:
Head-length. 3-6 mm.""!„ 6-0 mm. I T-, ,
_ „ >Embryos.„ 7-0 mm. f J
8-0 mm. J„ 8-0 ran. Just-hatched young.
The fully formed chondrocranium described belongs to anembryo of a head-length of 8-0 mm.; the head of the just-hatched lizard also measured the same. Alizarin transparenciesof 8-0 mm. embryo and just-hatched young, van Wijhe'spreparations of all the stages and wax models of the ehondro-cranium of the embryonic stages have been made.
I -wish, to express my sincere thanks to Professor E. S. Good-rich for having gone through the paper and for helpful criticism,and also to Professor A. Subba Eau for lending Gaupp's papero n L a c e r t a from his personal library.
OBSERVATIONS
l a . E m b r y o , H.-L. 3-6 mm. (Text-fig. 1).In the occipital region, the occipital arch (Text-fig. 1, oca)
arising from the basal plate (bp) is unconnected by a tectum.The otic capsule is not yet formed but for the slight formation
of cartilage in the region of the future recessus scaiae tympanilaterals (metotic fissure). The independent cochlear cartilage
THE CHONDROCEANIUM OF CALOTES VERSICOLOB 239
(pc) is united with the basal plate by a basicochlear commissure;while on one side a prefacial commissure is noticed, on the otherthe facial root is unenclosed. The basal plate shows one hypo-glossal foramen on one side and two on the other.
TEXT-FIG. 1.
The chondrocranium of a 3-6-mrn. (H.-L.) embryo of Calotesvers ieo lor (Baud.), X50 (model). 6c/, basicranial fenestra;bp, basal plate; cse, commissura sphenoetkmoidalis; fm, fenestranietoptica; hyf, hypophysial fenesfcra; lore, left orbital cartilage;nc, cartilage of nasal capsule; oca, occipital arch; of, optic fenes-tra ; ore, right orbital cartilage; pa, pila antotica; pc, prominentiacochlearis; pm, pila metoptica; por, preoptic root; sn, septumnasi; tc, trabecula communis.
There is an interesting feature in the condylar region. Thenotochord is dorsal to the basal plate. The occipital arch isunited with the basal plate and represents the neural arch(Id) of the proatlas vertebra; the hypocentrum (bv) of thisfuses with the basal plate to form the single condyle. Normallythis must fuse with the pleurocentrum (id) behind it to form avertebra. However, in lacertilians, in the condylar region thispleurocentrum fuses instead with the pleurocentrum of theatlas and both with the same of the axis vertebra which formsi,he odontoid process. That the occipital condyle is formed by
240 £. S. BAMASWAMI
the hypoeentrum of the proatlas, which at least is temporarilyunited with its own pleurocentrum, is seen in this stage ofCalotes (Text-fig. 15 F). Here the fusion is seen between thebasal plate (inclusive of the hypocentrum of the proatlasvertebra), the pleurocentrum of proatlas and atlas vertebraeand that of the axis. A similar phenomenon has been describedin Eumeces, where Eice (1920) recorded the confluence ofthe cartilage of the odontoid process and the basal plate. Theoccipito-atlantal joint is, therefore, intravertebral in lacertilians.
In the orbitotemporal region the orbital cartilages (Text-fig.1, ore) are paired and separate. Extending from the posteriorregion of the pila antotica (pa) with which each orbital cartilageis united, it ends anteriorly as a short projection in front of itsunion with the preoptic root (jaor) and shows a number offenestrae due to absence of chondrification in the wall. In frontof the pila antotica (pa) arising from the lateral aspect of thecrista sellaris, the pila metoptica (pm) of each side unites withthe orbital cartilage and between the two pilae there is themetoptie fenestra, (/m) in which the oculomotor nerve gainsexit either through an incomplete or complete orifice in the pilametoptica (pm). The trochlear nerve gains exit between thepila antotiea and the orbital cartilage, i.e. in the dorsal part ofpila metoptica or through an orifice in the orbital cartilage. Theabducens nerve passes out anteriorly to the incisura prooticaand becomes extracranial in the metoptie region.
The trabeeula commnnis (tc) formed anteriorly to the hypo-physial fenestra Qiyf) is continuous with the unfenestrated nasalseptum (sri); the orbital cartilage widens in the region of thenasal septum and unites with the trabecula by means of thepreoptic root (por). Further anteriorly, the sphenethmoidcommissures (cse) unite the orbital cartilages with the nasalcapsule (nc).
A parietotectal cartilage is feebly represented.A sclerotic cartilage is formed.The processus pterygoideus is still in a dense mesenchymatous
condition and a processus ascendens is not formed, so also thebasitrabecular process; a meniscus pterygoideus is recognizableas a deep mass of mesenchyme.
THE CHONDEOCRANIUM OP OALOTES VEBSIOOLOE 241
Meckel's cartilage is well developed, a feature also noticed inother lizards.
Ib. Embryo , H.-L. 6-0 mm. (Text-fig. 2).It was not possible to secure stages between the previous and
the present.
•pop .
TEXT-FIG. 2.
The chondroeranium of a 6'0-mm. (H.-L.) embryo of Calotesvers icolor (Daud.)> X50 (model); otic capsules and a part ofthe nasal capsule not included, aios, anterior portion of inter-orbital septum; cse, eommissura sphenoethmoidalis; hpf, hypo-physial fenestra; ios, interorbital septum; Ipm, left pila metoptica;l<por, left preoptie root; of, optic fenestra; ore, right orbital carti-lage; 2>a, pila antotica; pm, right pila metoptica; por, right pre-optio root; sn, septum nasi; tc, trabecula communis.
A tectum of the occipito-auditory region is not formed.The cochlear portion and the semicircular canal cartilages are
united by the basicochlear commissure as in the previous stage;a basivestibular commissure is not formed. The fenestraovalis and basicapsular fenestra are confluent. The foot plateof the columella is seen as an independent mass of cells. Be-tween the posterior semicircular canal portion and the occipitalarch, in the fissura metotica, the IX, X, and XI cranial nerves
242 Ii. S. RAMASWAMI
gain exit, while in the basal plate the two hypoglossal foraminaare seen. A prefacial commissure is also noticed.
In the orbitotemporal region, the oculomotor and trochlearnerves gain exit through the metoptic fenestra; the abducenscuts the base of the pila antotica and passes through a tunnelin the basal plate for a short distance. The crista sellaris unitesthe parachordals in the region posterior to the hypophysialfenestra.
An interorbital septum (Text-fig. 2, ios) has appeared whichposteriorly is continuous with the trabecula communis (tc) infront of the hypophysial fenestra (hyf). Anteriorly the septumforks and from the dorsal ends of the fork start the preopticroots ($or, Ipor) and each root is met by the orbital cartilage ofits side. The olfactory ends of the forks are joined by thesphenethmoid commissures (cse). Thus between the preopticroots and the sphenethmoid commissures, as it were, the anteriorportion of the interorbital septum (aios) has been added in thedura mater. The pila metoptica (jpm, Ipm) is paired and unitedwith the orbital cartilages (ore) as in the previous stage. There isa single large optic fenestra (of) between the interorbital septumand orbital cartilages. As in the previous stage, the orbitalcartilage does not project posteriorly to the metoptic pillar.
The unchondrified processus pterygoideus is shorter than inthe previous stage and the cartilaginous processus ascendens iswell developed with a free meniscus pterygoideus on its medialside. A basitrabecular articulation is also developed.
In the nasal region the nasal septum is well formed anddorsally it is united with the parietotectal cartilage. Thesphenethmoid commissure unites with the paranasal cartilageposteriorly.
The sphenethmoid commissure must unite with the antorbitalcartilage, but since the latter is not clearly demarcated, it isstated that the commissure unites with the paranasal cartilage.Between the paranasal and the parietotectal cartilages in a largegap the lateral nasal branch of the ethmoid nerve gains exit;thus, the epiphaneal foramen is not yet enclosed.
The nasal septum (sn), which is not continuous with theinterorbital septum (ios), shows ventrally a clubbed appearance;
THE OHONDROCRANIUM OP CALOTES VERSICOLOR 2 4 3
this thickening continues posteriorly and ends where it meetsthe interorbital septum. In L a c e r t a (Gaupp, 1900) andBumeces (Rice, 1920) it is noticed that the trabeeula com-munis continues anteriorly and unites with the base of the nasalseptum and could be easily differentiated from the interorbitalseptum by its rounded appearance. In C a 1 o t e s, unlike theprevious stage, the trabeeula communis cannot be differentiatedas in L a c e r t a or Bumeces .
The hyobranchial skeleton is laid down but will be describedlater (8-0 mm. stage). There is no connexion between the hyoidcornu and the columella.
I c. Embryo , H.-L. 7-0 mm. (Text-fig. 3).The cartilages of the occipital, otic, olfactory, the columella
auris and the hyoid apparatus are well formed and will bedescribed in the next stage.
A tectum synoticum plus posterior is noticed in this stageuniting the otic capsules and occipital arches. A short processusanterior tecti is given off from the tectum.
At the region the sphenethmoid commissure (Text-fig. 3, cse)unites with the interorbital septum (ios), the forked nature ofthe interorbital septum seen in the previous stage is lost, andthe two commissures, therefore, arise from a thick cartilage;from the dorsal end of the septum, the two preoptic roots, whichhave united together to form a pillar, arise. I have called thisthe preoptic pillar (pop). Prom the upper end of this pillar isnoticed the flooring cartilage for the brain, the planum supra-septale (ps) as in L a c e r t a (Gaupp, 1900) and Eumeces(Eice, 1920). From the posteroventral aspect of the planum thetwo orbital cartilages, now called taenia medialis (tme), proceedposteriorly, and at the region where the taeniae start from theplanum, there is an obliquely vertical pillar of cartilage (pios).This pillar, not noticed in previous stages, arises from the inter-orbital septum (ios) below, separating an anterior septal fenestra(/2) from a posterior optic fenestra (of). These paired taeniaemediales (tme) unite posteriorly; and slightly in front of this union,the united cartilago hypochiasmatica, subiculum infundibuliand pilae metopticae (cfisp), arising from the trabeeula communis
244 L. S. BAMASWAMI
(tc) in front of the hypophysial fenestra, unite •with the conjointtaeniae. Obviously the taeniae posterior to the united verticalcartilage referred to above represent the reminiscent orbital
TBXT-MG. 3.
The interorbital septal region of a 7-0-rnm. (H.-L.) embryo ofCa lo te s ve r s i co lo r (Daud.), x50 (model), aios, anteriorportion of interorbital septum; chsp, pillar formed by the unionof cartilago hypochiasmatica, subiculum infundibuli, and pilaemetopticae; cse, eommissura sphenoethmoidalis; f2, the largerseptal fenestra; ios, interorbital septum; Ion, lamina orbitonasalis;of, optie fenestra; pios, pillar from the interorbital septum to theposterior portion of planum supraseptale; <pma, processus maxil-laris anterior; pop, pillar formed by the fusion of the two preopticroots; ps, planum supraseptale; sn, septum nasi; to, trabeculacommunis; tme, taenia medians.
cartilage which connected the pilae metopticae and antotica inthe previous stage.
The incomplete fenestra behind the united vertical cartilage(chsp) and in front of the pila antotica represents the metopticregion.
THE CHONDEOCBANIUM OF CALOTES VEKSICOLOR 245
Id. Embryo , H.-L. 8-0 mm. (Text-figs. 11-14).The fully formed chondrocranium belongs to this stage.
1. The Basa l P l a t e and No toeho rd .The basicranial fenestra (Text-fig. 2, bcf) is noticed, as
already described, from the 3-6-mm. stage and is not formedby the resorption of cartilage in this region. The basicap-sular and basivestibular commissures are formed (also noted inthe previous stage) and the foramen ovalis is limited by thegrowth of cartilage in the ovalis region of the otic capsule. Inthe 3-6-mm. stage, the basicapsular fenestra was confluent withthe fenestra ovalis. I cannot say when exactly the otic capsulebecomes united with the parachordals, not having the stagesbetween 3-6 mm. and 6-0 mm.
From the basicranial fenestra, the basal plate (Text-fig. 11 ;Text-fig. 12, bp) gently rises up towards the foramen magnum(fma); anterior to the hypophysial fenestra (Text-fig. 12, hyf)the interorbital septum (Text-fig. 11, ios) forms a deep arch nearthe olfactory capsule before uniting with the nasal septum (sri).There is a broad prefacial commissure (pfc). The pila antotica(Text-figs. 11,12, pa) arises from the anterolateral corner of thebasal plate, and in this region the two sides are connected, infront of the basicranial fenestra (Text-fig. 12, bcf), by the cristasellaris (cs). The abducens nerve pierces the basal plate intern-ally to the pila antotica {pa), passes through a tunnel for a shortdistance, and then emerges in the basal plate by an orifice (fa).In the condylar region the notochord (nc) runs dorsally in thereniform condyle seen both in 7-0-mm. and 8-0-rnm. stages.This condyle is situated between two projections (Text-figs. 11,12, oc) of the basal plate and later the two projections andcondyle fuse to give rise to a monocondyle. Even in the adultCa lo tes , the line of fusion of the hypocentrum between thetwo exoccipital portions is clearly visible. In Eumeces Eice(1920) described a deep notch between two projecting condyle-Uke cartilages which he compared with the mammalian bicon-dyle;in L a c e r t a (Gaupp, 1900) the two projections are not soprominent.
246 L. S. RAMASWAMI
The notochord in Calotesis wedged in the basal plateexcept posteriorly, where it runs dorsally; where it entersthe odontoid process, it passes through the basal plate for avery short distance. Anteriorly it extends into the basicranialfenestra as far as the crista sellaris (not shown in my figures),as in other lizards.
2. The Occipital Eegion.The two principal occipital arches (Text-fig. 11; Text-fig. 12,
oca) are united dorsally above the foramen magnum (fma) bythe tectum synoticum (plus tectum posterius) (tsy) which alsoconnects the otic capsules. While three preoccipital archesspring from the basal plate on each side in front of the occipitalarch enclosing three hypoglossal foramina inLacer ta (Gaupp,1900), there are only two pairs of hypoglossal foramina (Text-fig. 11, hy) in Calotes. Between the otic capsule and theoccipital arch there is the jugular foramen (Text-figs. 13 A, 13 B,fj) for the exit of the X and XI cranial nerves and jugular vein(corresponding to the posterior portion of the fissura metotica ofLacer ta (Gaupp, 1900)). This jugular foramen is practicallyseparated from the more anterodorsal recessus scalae tympanilateralis (rsT) by the coming together of the ampullary portion(ppsc) of the posterior semicircular canal (psc) and the basalplate (bp); the connective tissue between these two is so thinthat the fissura metotica may be studied in two parts, viz. ananterior recessus scalae tympani lateralis and a posterior jugularforamen. Such a separation is also seen in Lacer ta (Gaupp,1900), while in Bumeces (Bice, 1920) is described an anteriorrecessus scalae tympani and a posterior foramen jugularis, beingformed by the apposition of the posterior ampullary promi-nence and the basal plate in front of the anterior hypoglossalforamen.
The jugular foramen itself is cut up into a larger anterior(Text-fig. 13 A,fj) and a tiny posterior portion (fj') between theoccipital arch and the otic capsule, the separation being due tothe coming together of otic capsule and the occipital arch. Thisdivision is of no significance since no nerves leave the craniumthrough the posterior orifice. An individual variation of the
THE CHONDROCRANIUM OF CALOTES VERSICOLOR 247
metoticfissure in L a c e r t a where it is completely cut into twoparts is also noted by Gaupp (1900, Fig. 4).
3. The A u d i t o r y Eegion.The otic capsules are large and are as long as the basal plate
(Text-figs. 13A, 1 8 B, bp); posteriorly there is the tecfcum synoti-cum united with the tectum posterius (Text-fig. 12, tsij). Fromthe anterior margin of the tectum, there arises medially a carti-laginous process, the processus anterior tecti (pat) supporting theendolymphatic organ. The united basicapsular and basivesti-bular commissures connect the basal plate with the otic capsule,leaving a large gap for the facial nerve (Text-fig. 11; Text-figs.13A, 13B, ff).
E x t e r n a l features.—Externally each otic capsuleexhibits the following features. The eoehlear portion (Text-fig.13 A, pc) is longer than in L a c e r t a (Gaupp, 1900); and, if aline is drawn connecting the facial foramen (ff) to the anteriorend of the recessus sealae tympani lateralis (rsl), a large portionof the eoehlear prominence is cut off as in Eumeces (Rice,1920). The topography of the remaining parts agrees fairly withthat in L a c e r t a and E u m e c e s . Laterally the three semi-circular canals, viz. the most clearly marked out anteriorsemicircular canal (asc) which is completely separated for ashort distance by a gap (gape) from the other two, the prominentposterior semicircular canal (psc) separated near the sinussuperior (ss) by the gap referred to above, and the lateral semi-circular canal (Isc) forming also a ridge-like prominence, arenoticed. Connected with the anterior or inferior openings of thesesemicircular canals, the ampullary prominences (pasc, plsc, ppsc)are also discoverable; the ampullary prominence at the inferioropening of the posterior semicircular canal is not very prominent.
From the prominence of the lateral semicircular canal (Isc) isseen a projection, the crista parotica (cp), with which anothercartilaginous structure, the processus paroticus ($p), is con-tinuous. Anteroventrally to these projections, there is the largefenestra vestibuli or ovalis (/o) in the eoehlear wall. An unchon-drified portion (uc) in the wall near the proeessus paroticus isalso noticed.
248 L, g. RAMASWAMI
On the medial aspect of the otic capsule (Text-fig. 13 B) alarge foramen acusticus anterius {fad) and a larger foramenacusticus posterius (fap) are noticed. Near the anterior foramenin the basal plate (bp) is the facial foramen (ff) referred to above.Anterior to this is the prominentia recessus utriculus (jjru), thewall of which unites with the basal plate forming the prefacialcommissure (pfc). The endolymphatic foramen (ej) is small,unlike that in Eumeces (Eice, 1920), and is posterior to theforamen acusticus posterius. Some unchondrified portions (uc)in the form of foramina are also noticed.
The I n t r a c a p s u l a r Cavity.—The cavity of theauditory capsule shows the same features as that of Lace r t a(Gaupp, 1900) or Eumeces (Eice, 1920). The main cavity isdivisible into an anterior smaller cavum vestibulare anterius(Text-fig. 15 A) and a larger posterior cavum vestibulare posteri-us, the two being separated by a septum intervestibulare (si).This septum shows two orifices normally in lizards, viz. aposterior median which permits the utrieulus lying in thecavum vestibulare posterius to communicate with the recessusutriculus in the cavum vestibulare anterius and an anteriorlateral foramen which is closed by a membrane. In Calotes ,however, the median one is not an orifice since it is not limitedby cartilage, while the lateral is normal.
The recessus ampullae of the anterior (raa) and lateral (ral)semicircular canals are at different levels from the utricularrecess (ru) in the cavum vestibulare anterius and lead into theanterior orifices of the canals respectively (in the figure only oneis seen, aoa). The roof of the cavum vestibulare anterius is,therefore, formed by the septum semicireulare anterius (sasc) tillthe latter separates itself from the cavum to run dorsally tothe gap referred to above (Text-fig. 15c).
The cavum vestibulare posterius is a spacious chamber intowhich the cavum cochleare (cc) opens anterodorsally. Postero-ventrally, the cavum vestibulare posterius gives rise to the reces-sus ampullae posterius (rap) which continues into the inferioropening of the posterior semicircular canal (Text-fig. 15 c, ipsc).The posterior opening (Text-fig. 15 c, opl) of the lateral semi-circular canal (Isc) in the posterior region of the cavum vestibulare
THB OHONDROGRANITJM OF OALOTBS VERSI0QBQB 2 4 9
posterius is above the posterior ampullary recess near the sep-tum of the posterior semicircular canal (spsc). On the posterioraspect of the septum semicirculare posterius (Text-fig. 15 D,spsc) the superior orifice of the posterior semicircular canal (osp)and the foramen pro sinu superior (fps) are noticed. In therecessus sinus superior (Text-fig. 15 a, rss) the posterior orifice(opa) of the anterior semicircular canal is noticed and in thisregion the posterior and anterior semicircular canals merge intothe sinus superior.
A brief reference may be made to the cartilaginous canals.The three semicircular canals are separated from the cavumvestibulare by septa; the septum of the anterior canal is hori-zontal (Text-fig. 1 5 A, sasc) and forms the roof of the cavumvestibulare anterius as in L a c e r t a , but slightly anterior tothe region of the posterior opening of the lateral semicircularcanal, the otic capsule "wall (Text-fig. 15 c, slsc) forms the roofof the cavum vestibulare posterius, the membranous anteriorsemicircular being enclosed in its own canal (asc) and thus beingseparated from the otic capsule by a gap. Posteriorly, however,at the region of the sinus superior, the semicircular canal (Text-fig. 1 5 B, asc) again joins the cavum vestibulare posterius toopen into the recessus sinus superior (rss). The septum of thelateral semicircular canal (Text-figs. 15 A, 15 B, slsc) is obliquelyvertical and longitudinal; it partly forms the inner wall of thecavum vestibulare posterius. It anteriorly meets the septumintervestibulare (Text-fig. 1 5 A, si) on the lateral side andprojects into the posterior part of the cavum vestibulare anteri-us. The posterior extension of the septum (Text-fig. 15 c, slsc)is seen in the region where the lateral semicircular canal opensinto the cavum vestibulare posterius by its posterior orifice(opl). The septum of the posterior semicircular canal is short(Text-figs. 15 c, 15 D, spsc), vertical and transverse and formsthe posterior inner wall of cavum vestibulare posterius. Theanterior face of this septum limits the posterior opening of thelateral semicircular canal, while its posterior faces the sinussuperior. In this posterior semicircular septum is the foramenpro sinu superior (Text-figs. 15 c, 15 i>,jps), one edge of which islimited by the otic capsule wall. At the region where the lateral
250 i. S. RAMASWAMJ
ct.
IX
TEXT-FIG. 4.
The region of the columella auris of a 8-0-mm. (H.-L.) young ofC a l o t e s v e r s i c o l o r (Daud.) to show the relation of blood-vessels and nerves; aci, arteria carotis interna; bpp, basipterygoidprocess; cp, erisfca parotica; cps, cartilaginous connexion betweenstapes and the insertion plate of columella; ct, chorda tympani;epl, the extrapleetral-parotic (processus) ligament; fro, foramenrotundum; /}/, hypoglossal foramina; hyn, hypoglossal nerve; Ja,Jaeobson's anastomosis; mus. part of stylomastoid muscle spanningthe extrapleetral and crista parotica; pd, ligamentary processusdorsalis; pi, cartilaginous processus internus; pie, pars inferior ofinsertion plate; pp, processus paroticus; pse, pars superior of in-sertion plate; q, quadrate; sa, stapedial artery; st, stapes; vcl,vena capitis lateralis; 7g, facial ganglion; 7h, hyomandibularbranch of facial nerve; 7p, palatinus facialis; IX, glossopharyngealnerve; IXg, ganglion on the I X ; X, vagus nerve.
THE CHONDKOCRANIUM OP OAL.OTES VERSIOOIiOR 251
semicircular canal enters the cavum vestibulare posterius thereis a short projection of cartilage (Text-fig. 15 c, ise) separatingthe inferior orifice of the posterior (ipsc) and the posterioropening of the lateral semicircular canals (opt).
The foramen perilymphaticum noticed in the posterior wallof the cavum cochleare faces into the fissura metotica. LikeL a c e r t a , the recessus scalae tympani of Calotes showsthe same arrangement: the recessus scalae tympani medialia(covered over by connective tissue) and the recessus scalaetympani lateralis (covered over by secondary tympanic mem-brane) and the IX nerve pierce both to gain exit.
The Columella Auris.—In the fenestra vestibuli(Text-fig. 11; Text-fig. 1 3 A, fo) fits in the footplate or stapes(st) of the columella auris, a product of the visceral arch. Theinsertion plate (Text-fig. 11; Text-figs. 16 B, 16 c, ip) which fitsinto the tympanic membrane is connected with the stapes by acartilaginous bar (the whole being called extracolumella) andshows the following projections: a long cartilaginous processdirected anteroventrally—the pars inferior (Text-fig. 13 A;Text-fig. 4, pie) and the part of the plate which is postero-dorsal to the connecting piece of cartilage (Text-figs. 11, 1 3 A,16 B; Text-figs. 4, 5, cps)—-the pars superior (Text-fig. 1 3 A;Text-fig. 4, pse). From the pars superior there are two shortcartilaginous projections: one directed towards the quadrate—the processes accessorius anterior (Text-fig. 5, paa) from whicha thin ligament arises and is inserted to the quadrate, and aposterior—the proeessus aecessorius posterior (pap). Prom thisposterior process, no connexion either cartilaginous or liga-mentary is noticed with the ceratohyal, unlike what is describedby Fuchs (1907), Kunkel (1912), and Shiino (1914) in variousreptiles. In addition, starting from the pars inferior and passingover the pars superior there is a thick ligament (Text-fig. 4,epl) which meets the proeessus paroticus (pp) at the regionwhere the proeessus dorsalis {pd) (see below) unites with theformer. The chorda tympani (ct) passes dorsolaterally tothis ligament. There is also a muscle (mus) arising from theinsertion plate (from the pars superior region) and gettinginserted to the crista parotica (cp) along with the stylohyoid
NO. 347 S
252 Ii. S. BAMASWAMI
muscle. Such a muscle is also noticed by Brock (1932) inLygodaetylns.
No reference is made by Gaupp (1900) to these ligamentaryconnexions. Rice (1920) described in Eumeees a paroticligamentary connexion (with the chorda tympani passing later-ally to this) and Fuchs described a connexion between theprocessus accessorius anterior and the quadrate. Versluys(1903) described a ligamentary connexion between insertionplate and parotic process in P a c h y d a c t y l u s ; in Lygo-d a c t y l u s (Brock, 1932) a transient cartilaginous connexionwith the parotic process with which the ceratohyal also unitedis noted. In Agama (Brock, 1932) and Varanus (Bahl,1937) the parotic ligamentary connexion is described, andVersluys (1903) in his schematic figure of the columella auris forlizards shows a ligament arising from the pars inferior (as inVaranus , Bahl, 1937) and reaching the processus paroticus orintercalary. In Amphisbaena Versluys (1898) mentionedthe absence of this connexion.
From the connecting cartilaginous rod between insertionplate and stapes arises the cartilaginous processus internus(Text-fig. 13A; Text-fig. 4, pi) in Calotes and projectsanteroventrally towards the quadrate with which it articulatesas in L a c e r t a (Gaupp, 1900) and Agama (Brock, 1932).In Eumeees (Rice, 1920) it does not reach the quadrate. InL y g o d a c t y l u s (Brock, 1932) and adult Chalcides (Haas,1936) it is absent. According to Versluys (1898) the adult Scin-cidae lack it; in other lizards like Uroplates, Anguidae and em-bryos and adults of Geckonidae it is also absent (Versluys, 1903).
There is another ligamentary connexion in Galotes—theprocessus dorsalis (Text-figs. 11, 13A, 16B; Text-fig. 4, pd)uniting the connecting cartilaginous piece of the columella (cps)with the processus paroticus (pp). It arises dorsally from thecolumella at the region where the processus internus is given offventrally. Versluys (1903) described, in this connexion, howthe dorsal portion of the original cartilaginous processus dorsalisformed the intercalary or processus paroticus when it met thecrista parotica, while the connexion between the intercalary andcolumella remained as a ligament.
s te
S
TEXT-FIG. 5.
Transverse section of a 8-0-mm. (H.-L.) young of Oalotes vers i -color (Baud.) in the region of middle ear, x55. aci, arteriaearotis interna; art, articular; asc, anterior semicircular canaljbr, brain; cc, cavum cochfearis; ops, connecting cartilage betweenstapes and insertion plate; ct, chorda tympana; cva, cavumvestibulare anterius; fap, foramen acustioum posterius; fo, fora-men vestibuli; h7, hyomandibularis faoialis; Iso, lateral semi-circular canal; me, MeekeFs cartilage; me, middle ear; paa, pro-cessus accessorius anterior; pap, processus accessorius posterior;par, parietal; ps, pars superior of insertion plate; p7, palatinusfaoialis; q, quadrate; rsl, reeessus sealae tympani lateralis; sa,stapedial artery; si, septum intervestibulare; sg, squamosal; ste,supratemporal; tm, taenia marginalis; tso, tuberculum spheno-ooci-pitale; ut, utriculus; vcl, vena capitis lateralis; 3, oculomotornerve.
254 L. S. EAMASWAMI
The processus dorsalis is absent in Eumeces (Eice, 1920),Lygodaety lus (Brock, 1932), and adult Chalcides (Haas,1936). In Varanus (Bahl, 1937) also a processus dorsalis issaid to be absent; however, a ligamentary connexion in exactlythe same position as the processus dorsalis is drawn (p. 159,Text-fig. 13); but the chorda tympani bears no relation to this.Having examined Varanus , I am inclined to consider theligamentary connexion as a processus dorsalis, though thechorda tympani does not surround it from backwards.
The branches of the hyomandibular nerve (Text-fig. 4, 7h, Ip,ct), the jugular vein, and the stapedial artery (sa) bear typicalrelations with the processus dorsalis ($&), processus internus(pi), and the ligamentary pars superior-parotic connexion asdescribed inLacer ta (de Beer, 1937).
4. The Orbi totemporal Eegion.As in other lizards, the orbitotemporal region is characterized
by the absence of a roof. The trabeculae (Text-fig. 12, tr) run-ning anteriorly from the basal plate unite anteriorly to thehypophysial fenestra (hyf) forming the trabecula communis(tc). In La cert a (Gaupp, 1900) and Eumeces (Eice, 1920)the trabecula communis runs anteriorly under the interorbitalseptum. In Calotes i t stops short at the anterior end of thehypophysial fenestra. In Chelone Fuchs (1912) stated thatthe trabeculae did not enter into the formation of the inter-orbital septum.
The internal carotid artery becomes intracranial through thehypophysial fenestra.
The basipterygoid articulation is noticed as in Lacer ta(Gaupp, 1900) and Eumeces (Eice, 1920) between the basi-trabecular process of the trabecula (Text-fig. 11, Up) and thebroad meniscus pterygoideus cartilage (mp), which representsthe basal process of the pterygoquadrate. No connexion be-tween the meniscus cartilage and the base of the processusascendens (pas) is noticed in any of the stages of Oalotesstudied.
The interorbital septum (Text-fig. 11, ios) makes a sharp bendnear the olfactory region. Near the olfactory capsule, the sep-
THE CHONDRO CRANIUM OP CALOTES VEESICOLOR 255
turn shows an anterior smaller (fl) and a posterior larger (f2)septal fenestra. Connecting the interorbital septum anteriorlyand forming the anterior boundary of this large posterior fenes-tra there is the round bar of cartilage—the united preopticpillar (pop) uniting posterodorsally with the planum suprasep-tale (pis). From the ventral aspect of the posterior portion ofthe planum supraseptale there descends a vertical pillar (pios)which meets the interorbital septum below and forms the pos-terior boundary of the large fenestra (j2).
InLacer ta (Gaupp, 1900), in the region corresponding to thepreoptic pillar of Calotes, the anterior portion of the supra-septal cartilage is broad with a median depression; however,from the anterior portion of the planum there are two cartila-ginous projections, one on each side, as in Calotes (Text-figs.11, 12, apis). These two projections are just indicated inEumeces (Eice, 1920). From the posterodorsal edge of theplanum there arises in Lacer ta the taenia marginalis, which,however, is wanting in Calotes. A small projection fromthe lateral portion of the planum represents, in Calotes, theanterior end of the taenia marginalis (atm); similarly a smallprojection from the anterior margin of the otic capsule repre-sents the posterior reminiscence of this (ptm). In Lacer ta(Gaupp, 1900) the taenia medialis arising from the posteroven-tral edge of the planum supraseptale meets and fuses with thevertical pila antotica; it is also connected with two more pillars—the pila accessoria (connecting with taenia marginalis) andpila metoptica (uniting and forming the subiculum infindibuliand cartilago hypochiasmatica). In Calotes since there isno taenia marginalis, there is no pila accessoria; the taeniaemediates (tme) progress towards the hypophysial fenestra andfuse. Slightly anteriorly to this fusion the taeniae are met by ashort round obliquely vertical pillar (chsp) from the interorbitalseptum—the united cartilago hypochiasmatica, subiculuminfundibuli, and pila metoptica. In Lacer ta (de Beer,1937) that part of the taenia in front of the pila accessoriais called taenia medialis, while that behind it is the metopticpila. In Calotes, such a differentiation is not possible. Thetaenia posterior to this median cartilaginous pillar represents
256 Ii. S. EAMASWAMI
the reminiscence of the connexion of the taenia with the pilaantotica.
The various foramina in this region may now be recounted:
(i) the two septal fenestra (Text-fig. 11, $1, f2) anteriorly donot transmit anything.
(ii) the optic fenestra (of) is bounded anteriorly by thevertical pillar (pios) of the interorbital septum; below by theunited cartilago hypochiasmaticaj subiculum infundibuli, pilaemetopticae and interorbital septum, and dorsally by the taeniamedialis.
(iii) the metoptic fenestra (fm) is bounded anteriorly by thecartilago hypochiasmatica (plus subiculum infundibuli and pilaemetopticae), above by the posterior part of the taenia medialis,below by the trabeeula, and posteriorly there is no definiteboundary. The third and fourth cranial nerves take exit inthis fenestra.
(iv) the prootie fenestra (in front of incisura prootica, ipr) isno definite fenestra; it may be said that the pila antotica (pa)and processus ascendens (pas) bound it anteriorly, while belowit is bounded by the basal plate and behind by the auditorycapsule and prefacial commissure (pfc). Dorsally it is not limitedin Calotes , while in Lace r t a (Gaupp, 1900) the taeniamarginalis roofs it. It must, however, be noted that the trige-mlnal ganglion is lodged in an extracranial space, the cavumepiptericum, which is slightly posterior to the processusascendens in the ineisura externally to the skull wall.
A sclerotic cartilage is well developed.
5. The E thmoid Eegion .Since the topography of the cartilages in the nasal region
differs considerably from the descriptions of Lace r t a (Gaupp,1900) and Eumeces (Eice, 1920), I propose to describe indetail the olfactory region of Calotes .
The anterior sections of the nasal capsule in Calotes revealthat the fenestra narina (Text-fig. 14 c, an) is lateral and thispart of the olfactory sac, the cupola anterior (ca), is coveredover by the anterior parietoteetal cartilage. In L a c e r t a
THE CHONDEOCRANIUM OF OAIiOTES VEBSIOOLOR 2 5 7
(Gaupp, 1900) the median branch of the ethmoid nerve gets exitby the foramen apicalis situated one on each side in the cupolaanterior; the fenestra superior is above and posterior to eachapical foramen. In Calotes there is a gap between the nasalseptum and the parietotectal cartilage (Text-fig. 14 A; Text-fig.6 A, fa) and through this, the combined fenestrae apicales, theramuli medialis (me) come out. A fenestra superior is absent inCalotes. Supporting Jacobson's organ, the lamina transver-salis anterior (Text-figs. 14 B, 14 C, la) is noticed with its innerlimb united (clsn) with the unfenestrated septum nasi (sn). Afew sections posteriorly where Jacobson's organ is cut, it is seenas a discrete cartilage (Text-fig. 6B, la); no projection of itenters into the floor of Jacobson's organ as in Ablepharusand Ohalcides (Haas, 1935, 1936). In Calotes it dividesinto two, one partially embracing Jacobson's organ (Text-figs.14 B, 14 C; Text-fig. 6 c, ecc) and the other (apn) situateddorsally to this but laterally to the parietotectal cartilage; thislatter is an anterior extension of the paranasal cartilage. InLacer ta , the lamina transversalis anterior not only forms asupport for Jacobson's organ but also a complete ring ofcartilage (zona annularis) round it; in Calotes since the sidewall is incomplete in this region there is no ring formation.Further from the posteromedian part of the lamina transversalisanterior there arises in Lacer ta (Gaupp, 1900) the paraseptalcartilage (free from the nasal septum). It unites with theanterior portion of lamina orbitonasalis;in Calotes there isno paraseptal cartilage at all in this region. However, there isthe process corresponding to the ectochoanal cartilage (ecc).The nasal glands appear (Text-fig. 6D, In) in the gap betweenthe parietotectal (pte) and the anterior portion of paranasalcartilage (apri); the ramus lateralis (le) of the ethmoid nerve isassociated with these glands. This region would, therefore,correspond with the cavum conchale of Lacer ta . Theparanasal cartilage is unconnected with the parietotectal in thisregion nor does it form a concha nasalis by reduplication as inLacer ta and Eumeces. The lateral nasal glands are,therefore, not at all enclosed. In Text-fig. 6 E, the opening ofthe uact (din) from these glands into the olfactory sac is noticed.
258 If. S. BAMASWAMI
TEXT-BIGS. 6 A-6 F.
Consecutive transverse sections in the regioa of nasal capsule of8-0-mrn. (H.-L.) embryo of Ca lo t e s v e r s i c o l o r (Daud.).apn, anterior part of paranasal cartilage; din, duct enteringeavum nasale principale from lateral nasal glands; ec, recessuseetochoanalls; ecc, ectochoanal cartilage; fa, conjoint fenestraeapicalis; fn, fenestra narina; jo, Jacobson's organ; la, laminatransversalis anterior; Id, ductus nasolachrymalis; le, lateral eth-moid nerve; In, lateral nasal glands; max, maxilla; me., medianethmoid nerve; na, nasal; np, nasal process of premaxilia; 61,opening of nasolachrymal ducts; os, eavum nasale principale; osp,orifice between septum nasale and. parietotectal cartilage; pma,processns maxiUaris anterior; pn, paranasal cartilage; ptc,parietotectal cartilage; pv, prevomer; am, septomaxilla; sn,septum nasi; to, trabeciila commmiis; vp, vertical pillar.
THE OHONDEOORANIUM OP CALOTES VERSICOLOR 259
However, in the 8-0 mm. young, the opening of this duct isslightly posterior to the vertical cartilage formed by the unionof the paranasal and parietotectal cartilages. In this region(Text-fig. 6 E) the cavum extraconehale (ec) is also seen and thisis embraced by the paranasal cartilage (pn) having assumed theshape of a horseshoe. The lateral ethmoid nerve (le), as in theprevious figure, is external to the parietotectal cartilage (pto).Posteriorly (Text-fig. 6 F ) the parietotectal and paranasalcartilages unite forming a vertical pillar (vp) and still the ramuslateralis (le) is external to the cartilage. This pillar separatingthe olfactory from the extraconchal recess does not representthe fused posterior walls of the conchae nasales since the auditusconcha in all the Lacertilia is posterior to the epiphanealforamen; also it does not represent the crista semicircularis ofmammals since that is also posterior to the epiphaneal foramen.The paranasal cartilage continues posteriorly into the laminaorbitonasalis (Text-figs. 1 4 A, 14 c, Ion), the demarcating orificebeing the epiphaneal between the two.
The epiphaneal foramen (Text-fig. 1 4 A, fe) is peculiarlydisposed. The ramus lateralis nasi situated ventrally to thecommissura spheno-ethmoidalis (cse) becomes intracranialwhen the latter unites with the lamina orbitonasalis (Ion) andgets exit a few sections anteriorly. In L a c e r t a (Gaupp, 1900)and E u m e c e s (Eice, 1920) the ramus lateralis nasi gets outthrough the epiphaneal foramen and enters the cavum conchaleby its anterior opening, the auditus concha.
The olfactory nerve running dorsomedially to the spheneth-moid commissure enters the fenestra olfactorium aclvehens bygetting out through the foramen olfactoria evehens; this isexactly as in L a c e r t a (de Beer, 1937). The ethmoid nerve(ophthalmicus profundus V) enters the extracranial orbitonasalspace (cavum orbitonasale) ventrally to the sphenethmoidcommissure in Ca lo t e s and before entering the olfactory sacdivides into two; the ramulus median's enters by its own orificein the cartilaginous wall and not by the advehent opening asin L a c e r t a and gets out through the conjoint apical orifice inC a l o t e s . The passage of the lateral ramulus has been describedabove.
260 L. S. BAMASWAMI
The width of the nasal capsule in the posterior region couldonly be ascribed to the formation of an extracranial portionsince a concha nasalis is not formed in Ca lo tes .
The hinder part of the nasal capsule is free from the nasalseptum in L a c e r t a ; it is also free ventrally in Oalotes(Test-fig. 14 B) but attached to nasal septum dorsally by meansof the lamina orbitonasalis. The free olfactory floor in theposterior region formed by the lamina orbitonasalis shows aprojection by the side of the nasal septum. This projectionrepresents the reminiscence of the paranasal connexion (pps).
The lamina orbitonasalis shows two projections at differentlevels. The anterior one at about the level of the vertical pillarreferred to previously represents the processus maxillarisanterior (Text-figs. 14 B, 14 c; Text-fig. 6 F, pma). Arising fromthe posterior wall of the lamina orbitonasaKs on either side ofthe interorbital septum (ios) there is a short projection which Ihave called the posterior laminal process (pip)- This does notrepresent the posterior maxillary process, since in the 8-0-mm.stage this is noticed to arise from the posterior aspect of thelamina orbitonasalis and the posterior laminal process is alsopresent.
6. The P t e r y g o q u a d r a t e .The pterygoquadrate, it has already been pointed out, was
noticed as dense mesenchyme in the 3-6-mm. stage extendinganteriorly from the region where the future basitrabeculararticulation would be formed. The next and subsequent stagesshow that an anterior pterygoid process is not developed andthe proeessus maxillaris posterior of the lamina orbitonasalisrepresents the remnants of the ethmoid connexions of thepterygoquadrate. A processus ascendens is well formed (Text-fig. 11; Text-fig. 12, pas) and does not show any connexiondorsally with the otic capsule as in P l a t y d a c t y l u s (Hafferl,1921). In adult Va ranus (Bahl, 1937) the dorsal part of theprocessus ascendens is united with the otic capsule. Narayana-swamy Iyer (1943) also described a dorsal cartilaginous otic-ascendens connexion in Ca lo tes . There is a meniscus ptery-goideus (Text-fig. 11, mp) cartilage between the ventral portion
THE CHONDUOCRANIUM OF CALOTES VBESICOLOE 2 6 1
of the processus ascendeng and the basitrabecular projection(btp), representing the basal process of the pterygoquadrate.
The otic articulation of the pterygoquadrate is noticed as inother lizards (Lacert a Gaupp,1900; Bumeees Rice, 1920);the dorsal portion of the quadrate part of the pterygoquadrate(Text-fig. 11, oa) articulates with the crista parotica (cp) andthe processus paroticus (pp).
When the quadrate becomes ossified, the anterior crescenticportion of it forms an 'auditory cup' for the attachment of theanterior margin of the tympanic membrane.
The two rami of Meckel's cartilage (Text-fig. 7, me) are almoststraight circular rods united at the tip (sm), while posterior tothe region of articulation with the quadrate (aq) is the processusretroarticularis (pro). It is interesting to note that, as in otherlizards, Meckel's cartilage chondrifies much earlier than theneurocranium.
7. The Hyoid Appara tus .The dorsal part of the hyoid arch, viz. the columella auris, was
described in connexion with the otic capsule. The basihyal(Text-fig. 7, bh) gives rise anteriorly to a processus lingualis orentoglossus (pT), which enters the tongue, and to two lateralprocesses, one from each side, the hypohyal (Jih). From eachhypohyal (hh) extends the ceratohyal (eh) of its side. As alreadysaid, there is no connexion between the processus accessoriusposterior of the columella auris and the ceratohyal.
Prom the basihyal there project posteriorly, the first (cbrl)and second (cbr2) ceratobranchials; ceratobranchial 1 is articu-lated with the basihyal by a ball and socket arrangement(Gnanamuthu, 1937; Narayanaswamy Iyer, 1943). UnlikeLacer ta (Gaupp, 1900) and Eumeces (Eice, 1920) theceratobranchial 2 is a complete rod of cartilage and not observedto be in two parts.
II. Osteocranium of a j u s t -ha t ched young ofCalotes versicolor (Daud. ) , H.-L. 8-0 mm.
I am describing the cranial bones in a just-hatched youngof Calotes with a head-length of 8-0 mm. As already
262 I/, g. EAMASWAMI
IDC
•re t .
TBXT-KKJ. 7.
Meckel's cartilage and hyobranchial apparatus of a 8-0-mm. (H.-L.)embryo of Ca lo tes ve r s i eo lo r (Baud.), aq, articular facetfor quadrate; bh, basihyal; chrl, ceratobranciial I ; cbr2, cerato-branciual 2; ch, ceratohyal; hk, hypoiiyal; me, JVleckel's cartilage jpi, processne lingualia; pra, processus retroarticularis; sm,
> meckelii.
said, the adult skull has been described by Narayanaswamy Iyer(1943).
Membrane bones .
The nasal (Text-fig. 16 A, na) starts on each side o£ the nasal
process of the premaxilla (pmx) posterior to the conjoint apical
THE CHONDKOCRANIUM OP OALOTES VBKSICOIiOR 268
foramen. It is disposed on the parietotectal cartilage andextends as far as the epiphaneal foramen. In the adult, also,it is paired (Narayanaswamy Iyer, 1948). It is unpaired inVaranus (Bahl, 1937).
The frontal (Jr) arises over the lamina orbitonasalis posteriorto the epiphaneal foramen, medially to the prefrontals (prf) anddorsolaterally to the sphenethmoid commissure. The two bonesare disposed near each other on the preoptic pillar (Text-fig.16 o, pop), lateral to the supraseptal (ps), and end postopticallydiverging from each other. In the adult (Narayanaswamy Iyer,1948) the two frentals unite to form a single bone and the gapbetween the two bones in this stage is bridged by osseous tissue.
Each parietal (Text-figs. 16 A, 16 c, par) arises medially atthe posterior end of the diverging frontal and the cranial roofbetween the two parietals is bridged by connective tissue; in theregion of the anterior semicircular canal, the reminiscent taeniamarginalis projection from the otic capsule is dorsal and widelyseparated from the parietal and the bone ends on the cristaparotica (cp). In Lacer ta (de Beer, 1937) the frontals andparietals are associated with the taenia marginalis, but inCalotes, as already noted, this cartilage is not formed. Inthe adult Calotes (Narayanaswamy Iyer, 1948) the twoparietals unite to form a large bone with a median orifice—thepineal orifice. From the parietal there are two posterior parocoi-pital processes, each coming in contact with the exoccipital andquadrate of its side.
The septomaxilla arises dorsally to the union of the laminatransversalis anterior with the nasal septum and lies dorsally tothis cartilage and Jacobson's organ (see Text-fig. 6 B, sm). Itforms the floor of the olfactory sac (Text-fig. 16 B, smx) anddisappears where the cavum extraconchale enters the choana.In the adult (Narayanaswamy Iyer, 1943) the septomaxilla isdisposed ventrally to the nasal process of the premaxilla andmedially to the maxilla, in the olfactory region. In Chameleon(Haas, 1937) the septomaxilla is wanting.
The prefrontal (Text-figs. 16 A, 16-C, prf) arises on the postero-lateral surface of the nasal capsule, and in the region of theliberal nasal glands they form a lateral boundary for them.
264 Ii. S. BAMASWAMI
In the region of the lamina orbitonasalis and the sphenethmoidcommissures, each prefrontal shows two limbs, a flat andtransverse one externally to the frontal and a flat and verticaldepending downwards (towards the palatine) and investing theposterolateral face of lamina orbitonasalis. This vertical limb ofthe prefrontal lies medially to the nasolachrymal opening (Text-fig. 16 c, pnT). Between the two vertical limbs of the prefrontalsis noticed the orifice which is separated into right and left by theanterior end of the interorbital septum; the two spheneth-moid commissures arise from the dorsal end of this septum andproceed towards the lamina orbitonasalis. The orifice by theside of the nasal septum through which the ethmoid nerveenters the olfactory capsule is the posterior part of the cavumorbitonasale. In the young as well as in the adult (Narayanas-wamy Iyer, 1943), since a lachrymal bone is absent, the prefrontaltouches the maxilla on the side, and the latter bone, therefore,forms the external boundary of the nasolachrymal orifice.
The prevomer (Text-fig. 1 6 B, pv) appears as a single ossifica-tion below the nasal septum and also below the lamina orbito-nasalis. Posteriorly where the trabecula communis appears asa separated piece of round cartilage below the nasal septum,the anterior part of palatine appears on each side dorsally tothe now separate prevomers and a few sections posteriorly theprevomers disappear.
The palatine (Text-figs. 1 6 A, 1 6 B, 16 O, pal) arises behindthe prevomers and while forming the median boundary of thechoana, also gives rise to a maxillary process behind the laminaorbitonasalis. In this region the sections reveal, below thepalatine and externally to the palatine and maxilla, two roundcartilages; both these are posterior projections from the laminaorbitonasalis running parallel, and the lower one of themrepresents the processus maxillaris posterior. Similar isolatednodules of cartilage situated one above the other have also beennoticed dorsally to the palatine in the processus maxillarisposterior region of L a c e r t a (Gaupp, 1900). The inner borderof the palatine in Ca lo tes is noticed ventrally to a regionwhere the lamina orbitonasalis gives rise posteriorly to a bluntcartilaginous process.
THE CHONDEOOEANIUM OF CA1OTES VBESICOLOR 2 6 5
Extending from the posterior margin of the palatines are thetwo pterygoids (Text-figs. 16 A, 16 B, 16 c, pt). Each pterygoid isflat anteriorly as the palatine and has a ridge ventromedially,and in the region of the ectopterygoid (transpalatine) (Text-fig.16 B, ecp) shows an enlargement. Posterior to the basiptery-goid articulation (bpp) it becomes dorsoventrally flattened, and
P,t.
TEXT-FIG. 8.
Transverse section of 8-0-mm. (H.-L.) young of Ca lo te s v e r s i -co lor (Daud.) in the region of the ectopterygoid-pterygoid-coronoid articulation. x55. an, angular; ap, articular (withprearticular); c, coronoid; ct, chorda tympani; d, dentary; me,Meckel's cartilage; mS, ramus mandibularis V; pt, pterygoid; sa,supra-angular; tp, ectopterygoid (transpalatine).
it ends articulating with the ventral end of the quadrate {q).Between the palatine, pterygoid, maxilla, and ectopterygoid isthe mediopalatinal fossa (mpf).
The ectopterygoid (transpalatine) (Text-figs. 16 A, 16 B, ecp)spans the jugal-maxilla and the lateral limb of the pterygoid.At the region of articulation with the pterygoid, the coronoidprocess of the lower jaw (Text-fig. 8, c) also enters and the threebones articulate with thick connective tissue in between them.
The premaxilla (Text-figs. 16 A, 16 B, 16 o, pmx) is formed»jy the fusion of the two premaxillae; dorsally there is a large
266 h. S. HAMABWAMI
nasal process, which lies over the nasal septum and extendsmesially to the two nasals about half the length of the latter. Itcarries three teeth and also an anteriorly directed dentinal eggtooth (et). Ventrally there is a short median prevomerineprojection (Text-fig. 16 B).
On each side of the premaxilla the maxilla (Text-figs. 1 6 A,1 6 B, 1 6 C, mx) forms the outer ventral boundary of the orbitalong with the jugal; the anterior boundary of the orbit isformed by the facial process of the maxilla and the prefrontal.The maxilla also sends a process upwards between the prefrontaland nasal. This is the nasal process of the maxilla.
The dentition of the maxilla and premaxilla in the adultCa lo tes is described by Narayanaswamy Iyer (1943).
The fenestra narina (Text-figs. 16 A, 16 c, an) is lateral and issituated dorsally on the maxilla, but slightly posterior to wherethe latter meets the premaxilla.
The jugals are broad bones (Text-figs. 1 6 A, 16 c, ju); theanterior extension of each jugal is met with in the anteriororbital region, in association with the maxilla and in the regionof the ectopterygoid; the latter articulates with the jugal andmaxilla. Posterior to the maxilla, it broadens vertically formingthe posterior border of the orbit along with the postfrontal ;forming the supratemporal arcade, it ends dorsally to thequadrate where it is separated from the posterior process of theparietal by the squamosal and supratemporal.
The squamosal (Text-figs. 1 6 A, 1 6 B, 16 C, sq) forms theposterior portion of the supratemporal arcade and ends on thecrista parotica (cp) externally to the supratemporal.
The supratemporal (tabular, Narayanaswamy Iyer, 1943)(Text-figs. 1 6 A, 1 6 C, ste) arises over the crista parotica in-ternally to the squamosal and runs on the ventrolateralaspect of the posterior process of the parietal. The bone inthe adult is not associated with the prootic as in V a r a n u s(Bahl, 1937).
The postfrontal (Text-figs. 1 6 A, 1 6 B, 1 6 C, pfr) forms alongwith the lateral supraorbital extension of the frontal andparietal the posterior boundary of the orbit. Each postfrontalhas three projections, one dorsal meeting the fronto-parietal
TEXT-FIGS. 9 A, 9 B .
The lower jaw ofa8-0-nim. (H.-L.) young of Ca lo tes ve r s i co lo r(Daud.), 9 A, outer aspect; 9 B , median aspect, ang, angular;art, articular (with prearticular); cor, coronoid; den, dentary;me, Meckel's cartilage; orl, orifice for the lateral cutaneousbranch of mandibular V; or2, orifice for the main trunk of alveo-laris inferior nerve; pr, prearticular part of articular; sa, supra-angular; spl, splenial.
p r 1 f,v.
10a 10b
pat .TEXT-FIGS. 10 A, 10 B.
Otic capsule of a 8-0-mm. (H.-L.) young of Ca lo tes ve r s i co lo r(Daud.), (alizarin preparation); 1 0 A, inner view; 1 0 B , outerview, asc, anterior semicircular canal; bp, basal plate; cp, cristaparotica; ef, foramen endolymphaticus; epo, epiotic; exo, exocci-pital; fa, foramen acusticum; ff, facial foramen; fj, foramenjugulare; fro, foramen rotundum; fv, fenestra vestibuli; gape, gapbetween the anterior and the other semicircular canals; hf,hypoglossal foramina; op, opisthotie in the lateral semicircularcanal region; op", opisthotie in the posterior semicircular canalregion; pat, processus anterior tecti; pc, prominentia cochlearis;pr', prootic outside the otic capsule; pr", prootic in the anteriorsemicircular canal region; psc, posterior semicircular canal; so,supra-occipital; no, unossified parts.
NO. 347 T
TE
XT
-PIG
.
The
ch
ondr
ocra
nium
of
a
8-0-
mm
. (H
.-L
.)
embr
yo
ofC
alo
tea
ve
rsic
olo
r (D
aud.
), a
ide
view
of
mod
el,
x3
5;
Meo
kel'a
ca
rtil
age
and
the
rig
ht
otic
ca
psul
e ar
e n
ot
incl
uded
, ai
oa,
ante
rior
po
rtio
n of
int
eror
bita
l se
ptu
m;
apis
, an
teri
or
proj
ecti
on f
rom
th
e pl
anum
su
pra
sep
tale
;aq
, ar
ticu
lar
face
t fo
r q
uad
rate
; as
c, a
nter
ior
sem
icir
cula
rca
nal
; ai
m,
ante
rior
pro
ject
ion
of t
acni
a m
argi
nali
a;
bp,
basa
l p
late
; U
p, b
asit
rabe
eula
r pr
oces
s;
ca,
cupo
la
an-
teri
or ;
chs
p, u
nite
d ca
rtil
ago
hypo
chia
sina
tica
, su
bicu
lum
infu
ndib
uli
and
pila
e n
ieto
pti
cac;
cp,
cri
sta
par
oti
ca;
cps,
cart
ilag
e co
nnec
ting
st
apes
w
ith
inse
rtio
n p
late
; cs
e,co
mm
isau
ra e
phcn
oeth
moi
dali
s; P
.CC
, ect
ocho
anal
car
tila
ge;
fl,
ante
rior
fe
nest
ra
in
inte
rorb
ital
se
ptu
m;
JS,
larg
erfe
nest
ra
in
the
sam
e;
ff,
faci
al
fora
men
; fi
n,
fene
stra
met
op
tica
; fi
rm,
fora
men
mag
nu
m;
Jo, f
enes
tra
ves
tib
uli
;ga
pe,
gap
be
twee
n th
e an
teri
or
and
othe
r se
mic
ircu
lar
can
als;
hf,
hyp
oglo
ssal
for
amin
a;
ins,
reg
ion
whe
re
the
inte
rorb
ital
sep
tum
con
tinu
es i
nto
th
e na
sal
sep
tum
; io
s,in
tero
rbit
al s
eptu
m;
ip,
inse
rtio
n p
late
of
extr
a-co
lum
-
11.
ella
; ip
r,
inci
sura
p
roo
tica
; Io
n, l
amin
a or
bito
nasa
lia;
Isc,
lat
eral
sem
icir
cula
r ca
nal
; ta
p, m
enis
cus
pte
ryg
oid
eus;
oa,
otic
art
icul
atio
n of
qu
adra
te;
oc,
occi
pita
l co
nd
yle
;oc
a, o
ccip
ital
arc
h;
of,
opti
c fe
nes
tra;
pa,
pil
a an
toti
ca;
pas,
pr
oces
sus
asce
nd
ens;
pas
c,
prom
inen
tia
ampu
llar
isof
th
e an
teri
or
sem
icir
cula
r ca
nal
; pat
, pr
oees
sus
ante
rio
rte
cti;
pa,
pro
min
enti
a co
chle
arb
; pi
, pr
oees
sus
do
rsal
is;
pfc,
pr
efac
ial
com
mis
sure
; pi
, pr
oees
sus
alar
is
infe
rior
;pi
os,
cart
ilag
iaou
s pi
llar
uni
ting
int
eror
bita
l se
ptu
m w
ith
plan
um
sup
rase
pta
le;
pis,
pl
anut
n su
pra
sep
tale
; pl
sc,
prom
inen
tia
ampu
llar
is o
f th
e la
tera
l se
mic
ircu
lar
esn
al;
pina
, pr
oces
sus
max
illa
ris
ante
rio
r; p
ne,
para
naaa
l ca
rti-
lag
e; p
op,
preo
ptic
pil
lar;
pp,
pr
oces
sus
par
oti
cus;
pps
e,pr
omin
enti
a am
pull
aris
of
th
e po
ster
ior
sem
icir
cula
rca
nal
; ps
, pr
oces
sus
alar
is s
uper
ior;
foe
, po
ster
ior
sem
i-ci
rcul
ar c
anal
; pi
c, p
arie
tote
ctal
car
tila
ge;
ptm
, po
ster
ior
par
t of
tac
nia
mar
gina
lia;
q, q
uad
rate
; ra
t, re
e^
ns
aeal
aety
mp
ani
late
rali
s; m
, se
ptum
nas
i; a
t, s
tap
es;
Inte
, ta
enia
,m
edia
lis;
tsy
, te
ctu
m s
yeot
icui
n.
cse. apis.
,lon»•pip.
•pr.
cp
nc. bo.TEXT-FIG. 12.
THE CHONDROCKANIUM OP CALOTES VERSICOLOR 271
suture, another ventral articulating with the jugal, while aposterior third not only articulates with the upper niar»in of thejugal but also with the squnmosal; the squajrinsa] arliedlafioii Lnoticed only in t]« adult condition and no( in Hie jotui;; (TVU-fig. 16 c). Thus th( superior iempornl arcli in eomplelerf im-teriorly by this bono.
Though in Agamids a poslfronful ih described as absent(Brock, 1932) when the superior temporal arch is formed b\ (hepostorbital, I call the bone in the Aganiid CaloU s, a post-frontal. According to Brock, the single bone found in thisregion of P a e h y d a c t y his and Mabnia is apposed (o thefrontal and parietal (a criterion according to Camp (192S) ofthe postfrontal), while in A gam a it is apposid to (ho parietalonly, and is therefore called (he postorbital. Following Camp,'the postorbital lies between postfrontal. parietal, squamosiland jugal in position ventral and posterior to postfrontal'. Sincein Calo tes the bone abuts against the suture between frontaland parietal, I have called it postfrontal.
TEXT-FIG. 12.
The ehondrocranium of a 8-0-mm. (H.-L.) embryo of Calotesvers ico lor (Daud.), dorsal view, x 35; the model is so arrangedthat the planum supraseptale is at right-angles to the otic cap-sules, apis, anterior projection from the pjantmi stipraseptsile;asc, anterior semicircular canal; aim, anterior projection oftaenia marginalis; hef, basicranial fenestra; bp, basal plate; chsp.united eartilago hypoehiasnuitica, subieuliim infunclibuli andpilae metoptieae; can, cavum orbitonasale; cp, crista parotiea; cs,erista sellaris; ex. eomniissura sphenoethmoidalis; ecc, ectocho-anal cartilage; fa, foramen abducens; gape, gap between anteriorand the other semicircular canals; hyf, hypophysial fenestra; ios,interorbital septum; ipr, incisura prootica: Ion, lamina orbitona-salis; Isc, lateral semicircular canal; nc, notochord; oc, occipitalcondyle; oca, occipital arch; pa, pila antotica; pas, processusascendens; pasc, prominentia ampullaris of the anterior semi-circular canal; pat, processus anterior tecti; pios, pillar betweenthe interorbital septum and planum supraseptale; pip, posteriorlaminal process; pis. planiim supraseptale; ppsc, prominentiaampuUaris of the posterior semicircular canal; ps, processus alarissuperior: psc, posterior semicircular canal; pne, pars superior ofestrapleetral: pirn, posterior part of taenia marginalis; q, quad-rate; sn, septum nasi; tc, trabecula communis; tme, taeniamedialis; tr, trabecula; tsy, tectum synoticum.
272 L. S. EAMASWAMI
pasc
-Ptfflc
-p-ss.
hf .TEXT-FIG. 1 3 A.
T E X T - M G S . 13 A AKD 13 B.
The otio capsule with adjacent basal plate of a 8-0-rnm. (H.-L.)embryo of C a l o t e s v e r s i e o l o r (Daud.), x50. 1 3 A, outerview, 1 3 B, median view of model, acs, anterior semicircularcanai; bp, basal plate; cp, crista parotica; cps, connectingcartilage between stapes and insertion plate of extracolumella; ej,foramen endolymphaticus; jaa, foramen acusticus anterius; jap,foramen acusticus posterius; ff, facial foramen; fj, foramen,jugulare; fj', posterior part of jugular foramen; fin, foramenmagnum; jo, foramen vestibuli; gape, gap between the anteriorand the other semicircular canals; hf, hypogloasal foramina; Isc,lateral semicircular canal; oca, occipital arch; paa, processusaccessorius anterior; pas, processus ascendens; pasc, prominentiaampullaris of the anterior semicircular canal; pc, prominentiacochlearis; pd, processus dorsalis; pjc, prefacial eommiasure;pie, pars inferior of extrapleetral; pin, processus internus; plsc,prominentia ampullaris of the lateral semicircular canal; pp,processus paroticus; ppsc, prominentia ampullaris of the posteriorsemicircular canal; pru, prominentia recessus utriculus; psc,posterior semicircular canal; pse, pars superior of the extra-
THE CHONDROCKANIUM OP CALOTES VEESICOLOR 278
U C
ptm
TEXT-FIG. 13 B.
plectral; ptm, posterior part of taenia marginalia; rsl, recessusscalae tympani lateralis; ss, sinus superior; st, stapes; we, un-chondrified areas in the otic capsule.
TEXT-FIGS. 14 A - I 4 C (pp. 274-6).The olfactory capsule of 8-0-mm. (H.-L.) embryo of Ca lo t e s
v e r s i c o l o r (Daud.), x50. 14A, dorsal view; 1 4 B , ventralview; 14 C, lateral view, an, anterior naris; apn, anterior part ofparanasal cartilage; ca, cupola anterior; chn, union of laminatransversalis anterior and septum nasi; en, cavum conchaie; cse,commissura sphenoethnioidalis; ecc, ectochoanal cartilage; fa,united foramina apicalis; fe, foramen epiphaniale; ios, inter-orbital septum; la, lamina transversalis anterior; Ion, laminaorbitonasalis; pi, processus alaris inferior; pip, posterior lanrinalprocess; pma, processus maxillaris anterior; pn, paranasalcartilage; pps, posterior part of paraseptal cartilage; ps, processusalaris superior; ptc, parietotectal cartilage; sn, septum nasi; vp,vertical process.
274 L. S. RAMASWAMI
The parasphenoid underlies the ventral surface of thehypophysial fenestra, leaving anteriorly a small foramen (Text-figs. 1 6 A, 16 B, fo), and runs anteriorly under the interorbital
•fa.
en .
-Ion.
se.TEXT-FIG. 14 A (see p. 273).
septum (r). The median part under the hypophysial fenestraalso extends tinder the basipterygoid processes (ipp), whiledorsally it is united with the basisphenoid (bs). In L a c e r t a(de Beer, 1937) the parasphenoid arises in two lateral and amedian centre which unite later. In the adult this bone under-goes fusion with the overlying basisphenoid and the compositebone is called 'sphenoid'.
In each eye-ball of Calotes there are twelve sclerotic bones.A quadratojugal, postorbital, and supraorbitals are absent;
also no osteoscutes are seen in Calotes.
THE CHONDROCRANIUM OF CALOTES VERSICOLOR 2 7 5
The prearticular (Text-fig. 9 B, pr) arises on the inner aspectof Meckel's cartilage and fuses with the cartilaginous articular(art); the chorda tympani which enters posteriorly to the quad-rato-meckelian articulation runs between Meckel's cartilage andarticular.
p i
-la.
se.
TEXT-EIG. 14 B (see p. 273).
The supra-angular (Text-figs. 9 A, 9 B, sa) is noticed on theexternal surface of Meckel's cartilage above the angular; theposterior portion of the dentary covers a portion of the supra-angular as seen in sections (see Text-fig. 8, d).
The angular (Text-figs. 9 A, 9 B, ang) arises on the ventro-median part of Meckel's cartilage and covers the internal
276 L. S. RAMASWAMI
portion of the prearticular, and the upper portion of the angularis also covered over by the dentary (den).
The splenial (Text-fig. 9 B, spl) arises on the middle portionof Meckel's cartilage medially and is anterior to the angular.
The eoronoid (Text-figs. 9 A, 9 B, cor) arises dorsomedially tothe splenial and forms the anterior limit of the supra-angular.
Orifices in the Lower J a w .1. The orifice in the dorsal aspect of the retro-articular
TEXT-FIG. 14 c (see p. 273).
process posterior to the quadrate articulation for the entry ofthe chorda tympani is mentioned above.
2. Between the supra-angular and articular portion, mediallyin front of the quadrate articulation, the ramus mandibularisV enters the lower jaw.
3. Just posterior to the dentary, in a notch in this bonelaterally, there is an orifice in the supra-angular for a lateralcutaneous branch of mandibular V (Text-fig. 9 A, orl).
4. Anterior to the splenial there is an orifice for the pas-sage of the main trunk of the alveolaris inferior (Text-fig. 9 B,or2).
5. A number ef small orifices in the lateral aspect of thedentary for smaller branches of the alveolaris inferior arenoticed.
THE CHONDROCRANIUM OF CALOTES VBKSICOLOE 277
The C a r t i l a g e B o n e s .The basioccipital (Text-fig. 1 6 B, bo) appears as dorsal and
ventral lamellae in the posterior region of the basal plate; theventral lamella extends and there is a gap between it and theparasphenoid (Text-fig. 1 6 B, pas) anteriorly. The notochordis still seen to be wedged in the basal plate. The cartilaginousprocess (tuberculum spheno-occipitale) arising from the ventralaspect of the basal plate (Text-fig. 5, tso) is not yet invaded bybone.
In the adult (Narayanaswamy Iyer, 1943) the basioecipital isseparated from the anterior 'sphenoid'.
The ossifications in the otic capsule and the tectum are clearlyseen. The demarcations between the anterior prootic, dorsalsupraoccipital (plus epiotic) and posterior exoccipital (plusopisthotic) are wide unossified areas in the capsule. However,in the adult these separating areas disappear.
The supraoccipital (Text-figs. 10 A, 10 B, SO) arises perichron-drally on the upper and lower aspects of the tectum connectingthe posterior portion of the otic capsules. The anterior partof the processus anterior tecti (pat) is left unossified and betweenthe parietals and the supraoccipital, on each side of the process,there is a gap where the cranial cavity is covered over by con-nective tissue. The epiotic (epo), with which the supraoccipitalis continuous, is noticed in the sinus superior region (the posteriorpart of the anterior semicircular canal (Text-fig. 10 A, asc) andthe superior part of the posterior semicircular canal (psc)) andextends medially as far as the inferior opening of the posteriorsemicircular canal, enclosing the endolymphatic foramen (efj.
The exoccipitals (Text-figs. 10 A, 10 B, exo) ossify perichon-drally in the two occipital arches and each exoccipital uniteswith the opisthotic of its side to form a composite bone—theoto-occipital. The extension of each opisthotic is as follows:posterior face of cochlear portion (Text-fig. 10 B, op), behindfenestra vestibuli and below the crista parotica and in theposterior part of lateral (Text-fig. 16 A, op') and inferior portionof posterior semicircular canal (Text-fig. 1 6 A; Text-figs. 1 0 A,10 B, op"). Dorsally to the anterior hypoglossal foramen theopistiiotic (Text-fig. 16 B, ope, exo; Text-fig. 10B , op, op", exo)
rap.
FIG. 15 A.
fjrC\
/ J I
/ ^
FIG. 15 C. FIG. 15 D.
Fio. 15 E.TEXT-FIGS.
FIO. 15r.
THE CHONDKOCKANIUM OF CALOTES VEHSICOLOR 279
unites with the exoccipital. The foramen rotundnm (Text-fig.16 B, fro) is bounded, when viewed in the ventral aspect of theskull, anteriorly by opisthotic, posteriorly by exoccipital (exo),laterally by both these, and medially there is the cartilaginousbasal plate. The opisthotic (Text-fig. 10 A, op") when viewed onthe medial aspect of the skull, forms the posterior boundary ofthe foramen rotundum (fro) and making an arch reaches thedorsal part of the exoccipital (exo).
TEXT-FIGS. 15 A-15 F.15 A. Anterior part of the otic capsule of 8'0-mm. (H.-L.) embryo
of Calotes versicolor (Daud.), model viewed from theposterior aspect, xSO. 15 B. Slightly posterior to fig. 15 A,viewed from the posterior aspect, x 50. 15 c. Posterior to fig.15 B, viewed from the anterior aspect, x 50. 15 D. Same as fig.15 c, viewed from the posterior aspect (only the outline positionof the anterior semicircular canal is shown), x 50. 15 B. Anterioraspect of the posterior part of the otic capsule, x 50. 15 F. Theoccipito-atlantic region of a 3-6-mm. (H.-L.) embryo of Calotesversicolor (Daud.), x70. aoa, anterior opening of the anteriorsemicircular canal; asc, anterior semicircular canal; bp, basalplate; cc, cavum cochlearis; cp, crista parotica; cvp, cavum vesti-bulare posterior; cvp', external aspect of eavum vestibulareposterior; hf, hypoglossal foramen; faa, foramen acusticumanterius;/erp, foramen acustieum posterius; fe, foramen endolym-phaticus; fls, lateral foramen in the intervestibular septum; fps,foramen pro sinu; fv, fenestra vestibuli; ipsc, inferior opening ofthe posterior semicircular canal; ise, incomplete septum; Isc,lateral semicircular canal; Isc', external aspect of lateral semi-circular canal; oa, occipital arch; opa, posterior orifice of theanterior semicircular canal; opl, posterior orifice of the lateralsemicircular canal; osp, superior orifice of the posterior semi-circular canal; pasc, prominentia ampullaris of the anteriorsemicircular canal; pat, pleurocentnim of atlas vertebra; 2mx>pleurocentrum of axis vertebra; pc, prominentia cochlearis; plsc,prominentia ampullaris of the lateral semicircular canal; ppsc,prominentia ampullaris of the posterior semicircular canal:psc', external aspect of the posterior semicircular canal; pu,prominentia utricularis; raa, recessus ampullaris of the anteriorsemicircular canal; ml, recessus ampullaris of the lateral semi-circular canal; rap, recessus ampullaris of the posterior semi-circular canal; rpsc, recessus of the posterior semicircular canal;rpu, recessus of the utriculus; rss, recessus sinus superior; ru,recessus utrioulus (in the eavum vestibulare anterior); sasc,septum of the anterior semicircular canal; si, septum intervesti-bulare; slsc, septum of the lateral semicircular canal; spsc,septum of the posterior semicircular canal; tm, posterior part oftaenia rnarginalis; uw, unchondrified wall in the otic capsule.
280 L. S. EAMASWAMI
The opisthotic is demarcated from the anterior prootic by anunossified part of the lateral semicircular canal above the fenes-tra vestibuli and in front of crista parotica.
Between the arch of the opisthotic (Text-fig. 1 0 A, op"), theepiotie above and the prootic anteriorly, there is an unossifiedarea (uo) in the otic capsule. The prootic is an ossification in theanterior part of the otic capsule. The extension of the prooticis as follows: anterior semicircular canal as far as the middle ofthe gap (gape) between it and otic capsule (Text-fig. 10 A, pr");lateral ampullary region, anterior border of fenestra vestibulienclosing the facial foramen (ff) and extending towards the basi-pterygoid process in the basal plate; medially it forms theposterior boundary of the foramen acusticum posterius (fa) (butseparated from the opisthotic by an unossified portion (MO)).
In L y g o s o m a (Pearson, 1921) the prootic is described asextending as far as the crista parotica.
The basisphenoid in C a l o t e s (Text-fig. 16 A, 6S) appears inthe crista sellaris, basitrabecular processes, and in the trabeculaenear the crista: the ossification, as already noted (cf. para-sphenoid), is dorsal to the parasphenoid and between this mem-brane bone and the basisphenoid laterally there is the parabasalor Vidian canal (Text-fig. 16 A, VC) through which the palatinusfacialis nerve and the internal carotid artery pass. In the adultthe basisphenoid fuses with the parasphenoid to form a'sphenoid', as already described.
In L a c e r t a (de Beer, 1937) the presphenoid, basisphenoid,exoccipitals, supra-occipital, the epi-, pro-, and opisthotics andparasphenoid fuse to form a composite bone—the os basilarecommune. In C a l o t e s the basisphenoid, parasphenoid, ex-and supra-occipitals, epi-, pro-, and opisthotics and pleuro-sphenoids fuse to form a composite structure.
In C a l o t e s the two orbitosphenoids (Text-fig. 16 A, OS) areossifications in the dorsal aspect of the taenia medialis.
A presphenoid is described in L a c e r t a (Gaupp, 1906) asan ossification in the posterior part of trabecula communis. Iam not able to see this in sections of 8-0-mm. young of C a l o t e sstudied.
The pleurosphenoid ossifies in the pila antotica.
THE OHONBROCRANIUM OF OALOTES VBRSICOLOR 2 8 1
Jit.
rf.
soc.pat.TEXT-FIG. 16 A.
282 L. S. EAMASWAMI
opeTEXT-FIG. 1 6 B.
THE CHONDROCRANIUM OF CALOTES VEESICOLOR 283
fr.
pnl.
TEXT-FIG. 16 C.TEXT-FIGS. 16 A - 1 6 C.
Osteocranium of a just-hatched (8'0-mm. H.-L.) young ofCa lo te s ve r s i co lo r (Daud.). 1 6 A, dorsal aspect. 16 B,ventral aspect. 16 c, lateral aspect, an, anterior naris; aq,articular facet of the quadrate; bo, basioccipital; bpp, basiptery-goid process; bs, basisphenoid; eh, choana; cp, crista parotica;cps, cartilaginous connexion between stapes and insertion plate;ecp, ectopterygoid; ep', epiotic portion on the posterior semi-circular canal; ep", epiotic portion on the anterior semicircularcanal; epi, epipterygoid; epl, ligament between processus paroticusand insertion plate; et, egg tooth; exo, exoccipital; fl, anteriorfenestra in interorbital septum; f2 posterior fenestra in interorbitalseptum; ff, facial foramen; fj, foramen jugnlare; fm, foramenmagnum; fo, a gap in the parasphenoid; fr, frontal ;fro, foramenrotundum; hf, hypoglossal foramina; ip, insertion plate of extra-pleetral; ju, jugal; loc, left otic capsule; mpf, mediopalatinal fossa;•mus, part of styloniastoid muscle spanning crista parotica and parssuperior of extraplectral; mx, maxilla; no, nasal; oc, occipital con-dyle; of, optic fenestra; ope, opisthotic part of exoccipital; op',opisthotic in the posterior part of lateral semicircular canal; op",opisthotic in the posterior part of posterior semicircular canal; os,orbitosphenoid ;pal, palatine ;par, parietal ;pas, parasphenoid; pat,processus anterior teoti; pc, prominentia eochlearis; pi, processusdorsalis; pfr, postfrontal; pi, processus internus; pmx, premaxilla;pnc, the preoptic pillar and nasal capsule visible between thefrontals; pnl, nasolachrymal passage; pop, preoptic pillar; pp,processus paroticus; pi', prootic in the extra-otic capsule region;pr", prootic in the semicircular canal region; prf, prefrontal; ps,planum supraseptale; psc, posterior semicircular canal; pt, ptery-goid; pv, prevomer; q, quadrate; r, parasphenoidal rostrum; roc,right otic capsule; soc, sopraoceipital; smx, septomasilla; sq,squamosal; st, stapes; ste, supratemporal; stf, supratemporalfossa; no, unossified areas; vc, Vidian canal.
HO. 347 V
284 L. S. RAMASWAMI
The epipterygoid (Text-figs. 16 A, 16 B, 16 c, epi) or columellaeranii arises as perichondral ossification in the processus ascen-dens. In the adult Calotes, as in the young stage studied, thedorsal end of the epipterygoid is connected by a ligament withthe ventral aspect of the parietal right in front of the supra-temporal, but Narayanaswamy Iyer (1943) has described acartilaginous connexion as in Varanus (Bahl, 1937). Ven-trally the club-shaped end sits in a fossa in the pterygoid. Thetrigeminal ganglion is slightly posterior to the epipterygoidin the cavum epiptericum (an extracranial space), and theophthalmicus profundus V runs medially and the other twobranches of the. trigeminal nerve externally to the epipterygoid.
The quadrate (Text-figs. 16 A, 16 B, 16 c, q) bone arises asperichondral ossification in the quadrate cartilage and is free,and, therefore, streptostylic.
The articular (see Text-fig. 5, art) is noticed as a circularossification round Meckel's cartilage in the processus retro-articular region. This bone undergoes fusion with an anteriormembrane bone, the prearticular. In Calotes the prearticularis present as a separate bone only in early stages.
No mento-meckelian ossification at the symphysis of therami of lower jaw is noticed.
The ossification in the first ceratobranchial is the cornubranchiale primum.
DISCUSSION.
In the posterior region of Calotes the basal plate showstwo condyles with a notch between them and the notochord runsdorsally to the basal plate as in La cert a (Gaupp, 1900). Inearly stages of Eumeces (Eice, 1920) and Sphenodon(Schauinsland, 1900) the notochord may be embedded posteri-orly in cartilage; in Chelone (Gaupp, 1900) it enters the basalplate ventrally. In Emys (Kunkel, 1912) and Crocodilus(Shiino, 1914) the notochord is completely embedded.
In Lacer ta (Gaupp, 1900) the intercondylar notch is notprominent, while in Eumeces (Eice, 1920) it is pronounced,and Eice homologized these condyles with the mammalianones. In the adult Calotes the monocondyle includes the
THE CHONDEOCBANIUM OF CALOTES VBRSICOLOE 285
proatlas, and the condylar region shows clearly this addition.Wedged in between the exoccipital (plus opisthotic) projec-tions, the condyle is demarcated by a thin groove on eachside.
This median condyle is the hypocentrum of the proatlasvertebra, while the occipital arches represent its neural arches.The pleurocentrum of this proatlas unites with the same of theatlas and axis vertebrae to form the odontoid peg. That thishappens is seen in the 3-6-mm. stage of Calotes where theoccipital region of the basal plate is in temporary confluencewith its own pleurocentrum (as happens normally in the vertebralregion) which is already fused with the pleurocentra of atlas andaxis vertebrae, the notochord projecting centrally from this.Later, a joint appears between the hypocentral condyle fusedon to the basal plate between the exoccipital projections andthe atlas vertebra. Thus the craniovertebral joint is intra-vertebral and intersegmental as in other Lacertilia (de Beer,1937).
In Eumeces (Kice, 1920) a temporary union of the odontoidtip (pleurocentrum) with the basal plate was recorded. While inLacertilia, Sphenodon, and Ophidia the condyle is hypo-central, the pleurocentrum forms the median condyle in Croco-dilia and Chelonia.
The fissura metotica is undivided in La cert a (Gaupp, 1900),while in Eumeces (Bice, 1920) the fissure is cut into two bythe close apposition of the posterior ampullary prominence andthe basal plate. The more anterior is the recessus scalaetympani lateralis, while the posterior one is the foramen jugularefor the exit of X and XI cranial nerves. Through the formerthe glossopharyngeal nerve comes out. In Calotes also thefissura is separated into two by the coming together of the basalplate with the prominentia ampullaris posterior with only athin connective tissue lamella separating them, in the region ofthe hypoglossal foramina. The posterior jugular foramen isitself divided into an anterior larger and a posterior smallerpart which transmits nothing. In the adult a part of therecessus scalae tympani lateralis becomes the fenestra rotunda,over which the secondary tympanic membrane is stretched, and
286 L. S. BAMASWAMI
through this the glossopharyngeal nerve gets out. Thisarrangement is as in other lizards.
The number of hypoglossal foramina varies; in Calotesthere are two as in Eumeces, P l a tydac ty lu s andSphenodon (four in early stages), and later stages of C h r y -semys ; in Lace r t a , Crocodilus, and early stages ofChrysemys there are three, and four in Tropidonotus .Eice (1920) has given a list of the number of hypoglossal fora-mina in various reptiles.
The septum intervestibulare divides the internal cavity of theotic capsule into an anterior smaller (cavum vestibulare anterius)and a posterior larger chamber (cavum vestibulare posterius)in lizards. In Calotes the median orifice is not limited asin Lacer ta . The utriculus establishes connexion with itsanterior portion by passing over the septum intervestibularetowards its dorsomedian aspect, i.e. internally to the septumsemicirculare laterale • (Text-fig. 15 A). This is unusual. Thelateral orifice is normally situated.
In the orbitotemporal region of Calotes the formation ofthe interorbital septum is interesting. In the earliest stagestudied (3-6 mm.) it is noticed that the preoptic roots areseparate and the orbital cartilages connect each preoptic rootwith the pila antotica of its side (Text-fig. 1); the pila metopticaunites with the orbital cartilage in its region so that a typicalfenestra metoptica is formed. In the next stage (6-0 mm.) ashort interorbital septum (Text-fig. 2) has appeared whichanteriorly shows forking. From the lower ends of this fork thetwo sphenethmoid commissures start, while from the upperthe two preoptic roots proceed and meet the orbital cartilages.The two pilae metopticae connect the orbital cartilages posteri-orly and there is no antotic connexion. In the 7-0-mm. stagethe forked nature of the interorbital septum is lost, and, there-fore, the sphenethmoid commissures' diverge from the ventralend of the interorbital septum (Text-fig. 3); the two preopticroots have united to form the planum supraseptale. Anadditional pillar reaching from the ventral portion of the inter-orbital septum to the posterior part of the planum separatesan anterior septal fenestra from a posterior optic. The paired
THE CHONDROCEANIUM OP CALOTBS VBRSICOLOR 2 8 7
nature of the metoptic pila is lost; the taeniae mediales arisingfrom the posteroventral border of the planum meet the unitedcartilago hypochiasmatica, subiculum infundibuli and pilaemetopticae. In the next stage (8-0 mm.) tho preoptic pillar iselongated and the ventral unpaired portion of the interorbitalseptum has increased in size.
In L a c e r t a (de Beer, 1930) the orbital cartilages do notunite with paired preoptic pillars and even in the earliest stage,(4-5 mm.) showing the planum supraseptale (which representsthe anterior portion of orbital cartilages), it is single; onlyposteriorly by means of the taenia median's, which representsthe orbital cartilages in this region, the trabecula is connectedwith the paired pila metoptica. In C a l o t e s , on the otherhand, the preoptic roots are separate and these are connectedwith the pila antotica by the orbital cartilages to start with,and later, when the interorbital septum appears and the eyesenlarge, the preoptic roots fuse to form a pillar, the two orbitalcartilages unite to form the planum supraseptale, and the poster-ior portion of the orbital cartilages (taenia medialis) fuse •withthe median pillar (united cartilago hypochiasmatica, subiculuminfundibuli and pilae metopticae). The antotic connexion is lostand the taeniae marginales are also absent.
In Angu i s (Zimmermann, 1913) the planum supraseptaleis composed of paired separate orbital cartilages.
The fenestra metoptica in C a l o t e s is incomplete in the8-0-mm. stage, there being no connexion between the pila metop-tica and pila antotica by a taenia medialis as in L a c e r t a (Gaupp,1900). In E u m e c e s (Eice, 1920) also the fenestra metopticais incomplete, the pila antotica being barely indicated.
The pila antotica ossifies, and it has been called the 'alarprocess' by previous workers (Siebenrock, 1892, 1894; Bahl,1937). • This is clearly the pleurosphenoid, which also becomesunited with the various bones in this region of L a c e r t a toform an 'Os basilare commune'. In Ca lo te s also a pleuro-sphenoid is noticed, but the composite sphenoid bone is separatefrom the basioccipital.
The ethmoid region of Ca lo t e s stands apart from otherlizards described. The lamina transversalis anterior is uncon-
288 t . S. BAMASWAMI
nected on its lateral aspect with the roofing parietotectalcartilage, so that a zona annularis, as seen in L a c e r t a , isabsent in C a l o t e s .
The nasolachrymal duct, however, opens into the choanalregion behind the lamina transversalis anterior, which is alsothe condition in L a c e r t a (Gaupp, 1900).
The lamina orbitonasalis unites with the anterior portion ofparanasal cartilage in C a l o t e s , and a concha nasalis, so charac-teristically seen in lizards, is absent in Ca lo t e s . In this itresembles S p h e n o d o n . Further, no lateral fenestra is seenin C a l o t e s , and in the side view the nasal septum andectochoanal cartilages are seen (Text-fig. 14 c). The lateralnasal glands are accommodated in a space—the cayum conchale,between the posterior portions of the paranasal and parieto-tectal cartilages; in other lizards the glands are enclosed in acartilaginous concha nasalis.
Starting from the median aspect of the lamina transversalisanterior and meeting the median wall of the lamina orbitonasalisis the paranasal cartilage in L a c e r t a , which is unconnectedwith the nasal septum. In Ca lo tes this cartilage is wanting;there is only a short projection from the median aspect oflamina orbitonasalis.
The lamina orbitonasalis is demarcated from the nasal capsuleby the epiphaneal foramen and the processus maxillaris anterioris seen anterolaterally from the lamina. While a posteriormaxillary process is not visible in the 8-0-mm. stage embryo, inthe young of Ca lo tes of the same head-length two cartila-ginous parallel projections run dorsally to the palatine from thelamina orbitonasalis. The more ventral of these is the processusmaxillaris posterior while the other is without significance. InL a c e r t a (Gaupp, 1906), also, on the dorsal aspect of thepalatine, isolated nodules of cartilage in line with the processusmaxillaris posterior are recorded.
In C a l o t e s , on the posterior aspect of the lamina orbito-nasalis, on each side of the interorbital septum, there is a smallcartilaginous projection, and I have called it the posteriorlaminal process.
The pterygoquadrate (Text-fig. 11) is represented as a
THE CHONDBOCEANIUM OP OALOTES VERSICOLOR 2 8 9
separate movable quadrate posteriorly, a processus ascendens(which ossifies into the epipterygoid) and a basal process (themeniscus pterygoideus; the metapterygoid of fishes) articulatingwith the basitrabecular process; no processus pterygoideus isnoticed. However, in earlier stages, from the region where laterthe processus ascendens appears, there is an anteriorly directedmesenchymatous strand representing the processus pterygoid-eus. This does not chondrify. In Lacer ta there is a processuspterygoideus united with the processus ascendens, which isalways separate from the quadrate, and in Eumeces (Eice,1920) the processus pterygoideus is independent of the processusascendens; in earlier stages of Eumeces the processusascendens and processus pterygoideus and quadrate are united.In Mabuia, Zonurus, and Eremias (Broom, 1903) thereis a persistent cartilaginous connexion between quadrate andepipterygoid. In Sphenodon (HowesandSwinnerton, 1901),Chrysemys (Shaner, 1926),and crocodile (Parker, 1883) theseprocesses are united with the quadrate cartilage. According toFiirbringer (1904), to ensure greater mobility of the jaw, thequadrate becomes separated off from its anterior connexions.Characteristically the quadrate of the snake is also free from allthese processes.
The columella auris shows, in the young 0 a 1 o t e s with thehead-length of 8-0 mm., an ossified stapes and a cartilaginousextracolumella. From the insertion plate which fits into thetympanic membrane there arise the characteristic processes: thepars inferior and pars superior. From the latter arise the pro-cessus accessorius anterior and posterior. Arising from the parssuperior there is a ligament passing into the processus paroticusand a muscle which is a part of the stylomastoid muscle insertedon the crista parotica.
From the processus accessorius anterior there is a ligamentattaching itself to the quadrate; such a structure is alsodescribed in some chelonians by Fuchs. From the connectingcartilaginous piece between the insertion plate and stapes inCalotes there arises the processus internus which articulateswith the quadrate and a ligamentary processus dorsalis whichmeets the processus paroticus.
290 L. S. RAMASWAMI
The processus accessorius anterior connexion with thequadrate is not noticed in Lace r t a (Gaupp, 1900) andEumeces (Eice, 1920).
Generally the processus aceessorius posterior or processusinterhyalis unites with the ceratohyal in early stages and thisconnexion may even persist in later stages. In early stages ofLacer ta (Hoffmann, 1889; Gaupp, 1900), Eumeces (Eice,1920), Tropidonotus (Eathke, 1830), and Crocodilus(Parker, 1883) the connexion is noticed. In Sphenodon(Howes and Swinnerton, 1901) the connexion is permanent.There may be a mesenchymatous connexion between the parsinterhyalis and ceratohyal in Chelonia (Bender, 1911; Smith,1914); in Emys (Kunkel, 1912), however, there is a ligamentrunning between the pars interhyalis and the retroarticularprocess of the lower jaw.
A processus dorsalis is noticed in Lacer ta (ligamentary,Gaupp, 1900) and Calotes. In Eumeces (Eice, 1920) andLygodac ty lus (Brock, 1932) it is absent. In Agama(Brock, 1932) it persists as a cartilaginous connexion. InV a r a n u s, topographically, a ligamentary processus dorsalis ispresent, though Bahl (1937) noted to the contrary. In Spheno-don (Howes and Swinnerton, 1901; Versluys, 1903) the dorsalprocess is united with the quadrate; in Tropidonotus anindependent chondrification acquiring connexion with thequadrate is homologized with the processus dorsalis (de Beer,1937). While it is absent in Chelonia (Kunkel, 1912), inCrocodilus it fuses with the quadrate.
A cartilaginous processus internus projects towards thequadrate in Calotes, and as in Lacer ta (Gaupp, 1900) thereis no union with the quadrate (see, however, de Beer, 1937,p. 225). In Eumeces (Eice, 1920) it is very short and inLygodac ty lus (Brock, 1932) it is absent. So also inSphenodon (Howes and Swinnerton, 1901), Tropido-notus (Parker, 1879), Emys (Kunkel, 1912), and Croco-dilus (Goldby, 1925).
The last ligamentary connexion is the one that starts from thepars superior of the insertion plate and gets inserted on theprocessus paroticus at the region where the processus dorsalis
THE CHONDROCRANIUM 01? CALOTES VEESICOLOR 291
ligament also meets it in C a 1 o t e s. The chorda tympani runsdorsolaterally to this ligament, while the stapedial artery runsmedially to the processus dorsalis. In describing this tendon,Eice (1920) recorded its presence in Eumeces (with thechorda tympani running dorsally to it) and noted: 'This "tendonof extracolumella" is carefully described by Versluys (1898)for Sphenodon and adult lizards; it was only lacking inAmphisbaena among the many lizards studied.' InVaranus Bahl (1937) described it running into the cristaparotica, but the chorda tympani had no relation either withthe processus dorsalis ligament or this. Probably on account ofthis, he denied the presence of a processns dorsalis. In Agama(Brock, 1932) there is the extracolumella-crista ligament, butthe chorda tympani does not loop round it. All the same Brocknoted: 'Prom the condition in Lygodacfcylus where there isa cartilaginous connexion between the extracolumella and thecrista parotica in early stages it may be judged that the ligamentof Agama, L a c e r t a , etc., is homologous with the cartila-ginous and Kgamentous connexion of the Geckos and the latterwould then be the more primitive condition.' In all the examples(see below) where such a ligamentary or cartilaginous (latero-hyal) connexion is noticed, the chorda tympani always runsdorsolaterally to it; while the ligarnentous connexion of0 a 1 o t e s and Eumeces may be homologous with the latero-hyal, that of Agama and Varanus must be consideredanalogous.
In Sphenodon, from the processus paroticus or intercalarythere is a laterohyal cartilage uniting with the extracolumellaenclosing a 'Huxley's' foramen between the processus dorsalisand the laterohyal; the chorda tympani runs laterally to it.There is in addition to this a ligament from the extracolumellato the crista parotica and the exact homology of this tendonwhen there is a permanent laterohyal connexion with the cerato-hyal becomes difficult, and Versluys assumed that the con-nexion of the hyoid arch has been secondarily regained. Asimilar laterohyal connects in Grocodilus (Versluys, 1903)th •! intercalary with the epihyal, which itself is in contact withthe extracolumella by means of the pars interhyalis; the chorda
292 L. S. BAMASWAMI
tympani runs laterally to the laterohyal (de Beer, 1937, PI. 141,fig. 17).
In Geckos -with the ligamentary connexion between theextracolumella and parotic process (which may be cartilaginousin early stages, e.g. L y g o d a c t y l u s (Brock, 1982, fig. 6 B))the ceratohyal is directly connected with the parotic process,with the chorda tympani bearing no relation to it (or by-passinglaterally to it, de Beer, 1937, PI. 141, fig. 13), apparently resem-bling a laterohyal. However, in early stages the extracolumellais connected both with the processus paroticus and ceratohyal.
A brief reference may be made to the muscle that arises fromthe pars superior and gets inserted on the crista parotica.Externally to the ligament referred to above, the muscle hasbeen noticed in L y g o d a c t y l u s also (Brock, 1932). It isnoted by the author that the muscle is a part of the stylomastoidand not depressor mandibulae as Versluys would have it.Having examined early and late stages of C a l o t e s , I am inagreement with Brock.
SUMMABY
1. In the earliest stage of Ca lo tes studied, the basal plateis confluent with the pleurocentrum of the atlas and axis verte-brae. Later, a joint appears between the hypocentral condyleand the first vertebra. This shows that, at least temporarily,the elements of the anterior sclerotomic hah0 in this regionare in continuity with the posterior in front as happens in thevertebral region. The occipito-atlantic joint is, therefore, intra-vertebral and intersegmental as in other Lacertilia.
2. The anterior semicircular canal is completely separated fora short distance from the remaining otic capsule. The gap isfilled with connective tissue.
3. The intervestibular septum shows a lateral foramen whichtransmits nothing and the utricular connexion between theanterior and posterior chambers passes posteriorly to themedian part of the septum and, therefore, a medial orifice is notformed.
4. The preoptic roots, the orbital cartilages, and metoptic pilaare paired in early stages; the orbital cartilage connects the
THE OHONDROCRANIUM OP CALOTES VERSICOLOR 298
preoptic root, pila metoptica and pila antotica dorsally. Laterthe two preoptic roots merge to form a median preoptic pillar,the orbital cartilages anteriorly unite to form the planumsupraseptale, while posteriorly also the orbital cartilages (taeniamedialis) unite at the region of the hypophysial foramen. Thisposterior united portion is met by a median vertical pillar(formed by the. fusion of cartilago hypochiasmatica, subiculuminfundibuli, and pilae metopticae) arising from the trabeculacommunis.
The single septal fenestra is divided into an anterior largerand a posterior optic by the formation of median interorbitalpillar from the ventral interorbital septum which meets theposterior portion of the planum supraseptale. The ventralportion of the interorbital septum is never noticed to be paired;the taenia marginalis is absent. However, short projectionsfrom the posterodorsal margin of the planum and from theanterodorsal face of the otic capsule represent the reminiscenceof marginalis connexion. A supratrabecular bar is absent.
5. In the nasal capsule, a concha nasalis is absent; therefore,the lateral nasal glands are unenclosed in a cartilaginouscapsule. The anterior portion of the paranasal cartilage uniteswith the dorsal portion of the lamina transversalis anterior, andthe latter gives rise to an eetochoanal cartilage, but a paraseptalcartilage is absent. On the ventral side, from the free medianmargin of the lamina orbitonasalis, there arises a short projec-tion which represents the posterior portion of the paraseptalcartilage.
6. The pterygoquadrate shows a free streptostylic quadrate,a processus ascendens which ossifies into the epipterygoid, aprocessus pterygoideus only in early stages, a basipterygoidarticulation by a free meniscus cartilage, and an otic articulationwith the crista parotica and processus paroticus by the quadrate.
7. The columella auris shows a ligamentary processus dorsalisconnexion with the processus paroticus, a cartilaginous pro-cessus internus which articulates with the quadrate, a processusaccessorius anterior which is connected with the quadrate bya ligament, and a ligamentary connexion between the parssuperior of the insertion plate and processus paroticus. The
294 h. S. RAMASWAMI
processus accessorius posterior-ceratohyal connexion was notnoticed. There is also a muscle (a part of M. stylohyoid)spanning the pars superior and crista parotica. The parssuperior-paroticus ligamentaiy connexion, with the chordatympani running laterally to it, is homologized with thelaterohyal of Sphenodon and the crocodile.
8. The hyoid apparatus shows a processus. lingualis andcornuhyale (paired hypo- and ceratohyals) arising from amedian basihyal and two pairs of ceratobranchials.
9. In the osteoeranium, the oto-occipital of each side isformed by the fusion of opisthotie and exoccipital, while thesupraoccipital is formed by an ossification in the tectum and itsfusion with the two epiotics formed in the sinus region of theotic capsule. The basioccipital and the composite 'sphenoid'are not united. The pleurosphenoid ossifies in the pila antotica.The epipterygoid is connected at its dorsal end with the parietalby a ligament, and ventromedially it is free from the meniscuscartilage. The frontals and parietals are paired in the stageexamined, and in the adult the parietals of each side fuse, asalso the frontals.
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Born, G., 1879.—"Die Nasenhohlen und der Thranennasengang der amni-oten Wirbeltiere, I", Morph. Jahrb., 5.
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Broom, R., 1903.—"On the development of the pterygoquadrate arch inthe Lacertilia", Journ. Anat. Lond., 37.
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Broom, R., 1924.—"On the classification of Reptiles", Bull. Amer. Mus.Nat. Hist., 51.
Camp, C. L., 1923.—"Classification of the Lizards", ibid., 48.Cope, E. D., 1892.—"The osteology of the Lacertilia", Proc. Amer. Philoa.
Soc, 30.Cords, E., 1909.—"Die Entwicklung der Paukenhohle von Lacerta agilis",
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1924.—Ibid., 4.Edgeworth, F. H., 1935.—"The cranial muscles of Vertebrates". Cambridge.El-Toubi, M. R., 1938.—"The osteology of the lizard Scincus scincus (L.)",
Bull. Fac. Sci. Egyptian Univ., nr. 14.Fuchs, H., 1907.—"Ueber die Entwicklung des Operculums der Urodelen
und des Distelidiums (columella auris) einiger Reptilien", Verh. Anat.Ges. Vers., 21.
1912.—"Uber einige Ergebnisse meiner Untersuchungen uber dieEntwicklung des Kopfskelettes der Chelone imbricata", ibid., 26.
Gaupp, E., 1900.—"Das Chondrocranium von Lacerta agilis", Anat.Hefte, 14.
1906.—"Die Entwicklung des Kopfskelettes", Hertwig's "Handbuchvergleich experim. Entwicklungs.", 3. Jena.
Gnanamnthu, C. P., 1937.—"Comparative study of the hyoid and tongue ofsome typical genera of reptiles", Proc. Zool. Soc. Lond., Part I.
Goldby, F., 1925.—"The development of the columella auris in Crocodilia",Journ. Anat. Lond., 59.
Goodrich, E. S., 1915.—"The chorda tympani and middle ear in Reptiles,Birds and Mammals", Quart. Journ. Micr. Sci., 61.
1930.—"The Structure and development of Vertebrates". London.Haas, G., 1935.—"Zum Bau des Primordialcraniums und des Kopfskelettes
von Ablepharus pannonicus", Acta Zool., 16.1936.—"Uber das Kopfskelett von Chalcides guentheri (Seps mono-
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THB CHONDKOCRANIUM OP CALOTBS VEBSICOLOE 297
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