Strand-line Pebbles in the mid-Hastings Beds and

the Geology of the London Uplands.

General Features. Jurassic Pebbles

by P. ALLEN

With an Appendix on the derived Jurassic Ammonitesby the late Dr. W. J. Arkell

Received 22 September 1958

CONTENTS

1. INTRODUCTION2. GENERAL FEATURES OF THE PEBBLE ASSEMBLAGES3. JURASSIC PEBBLES ...4. CONCLUSIONS

ACKNOWLEDGMENTSREFERENCESApPENDIX BY THE LATE DR. W. J. ARKELL ...

page 156157161163164164165

ABSTRACT: Evidence is presented supporting earlier suggestions that the detrituscarried to the Wealden basin by the 'northern river' consisted mainly of waste fromUpper Jurassic, Lower Carboniferous and Old Red Sandstone strata, and that thisreflects the changing stratigraphical succession exposed by denudation in the Londonarea during the deposition of the Hastings Beds. The Upper Jurassic contribution isdescribed in detail. I

1. INTRODUCTIONA PRELIMINARY ATTEMPT has already been made to map the solid geology ofthe London Uplands as they existed during Wealden times (Allen, 1954).The report stressed the importance of the evidence provided by the gradedpebble beds capping the Ashdown, Lower Tunbridge Wells and subsidiaryarenaceous formations. These pebble beds are basal conglomerates,marking the beginnings of major transgressions which resulted in thedeposition of overlying clay formations (Wadhurst and Grinstead). Theyare beach deposits: strand-line gravels spread over extensive areas by thenorthward-retreating coastlines of the Ashdown and Lower TunbridgeWells deltas (Allen, 1959; 1960). As the rising lake-waters drowned thelower reaches of the distributaries the levees crumbled away, freeing thepebbles to spread wider afield under the influence of more open watercurrents.

Nearly all the pebbles in the conglomerates seem to have originated inthe London Uplands. They were brought southwards in the short, steep'northern river', the main pass or 'head of passes' of which usually lay

1 Carboniferous, Old Red Sandstone and other components will be the subjects of later papers.

156

JURASSIC PEBBLES IN THE HASTINGS BEDS 157

somewhere in the longitude of West Wickham (Allen, 1954, 504). Petro­logical study should therefore give a broad idea, though a selective one, ofthe more resistant formations outcropping in the catchment area. Thegathering ground itself must have comprised a large area to the north of theThames, centred roughly on what is now Metropolitan London. Since thedatable pebbles are nearly all of Old Red Sandstone, Lower Carboniferousand Upper Jurassic rocks, these were presumably the chief formationsoutcropping in the Uplands (ef op, cit., 505-7).

Subsequent work on the pebbles, to be reported in this and succeedingpapers, confirms and extends these conclusions. Here, general features ofthe assemblages are first described; then the Jurassic components in moredetail.

2. GENERAL FEATURES OF THE PEBBLE ASSEMBLAGES

(a) Sampling

At an early stage it became evident that very large random samples ofcoarse conglomerate would be needed. The horizon chosen for intensivework was the Top Lower Tunbridge Wells Pebble Bed, and the area withinit the one-and-a-half-mile-wide tract running south from East Grinstead toPaxhill (Allen, 1954, text-fig. 1; 1959). There, the pebbles are biggest andmost abundant and the bed attains its greatest thickness. The tract seems torepresent a late Lower Tunbridge Wells distributary, partially obliteratedby the transgressing Grinstead Lake. Two localities were selected fordetailed investigation:

(1) Paxhill Park (356272).1 An overgrown 'hollow' in the roadside(B2028) shaw nearly opposite the entrance to 'Buxshalls', one milenorth-east of Lindfield. Three hundredweights of conglomerate wereobtained. This is probably the historic locality where Topley 'founda small fragment of an Ammonite' (1875, 84).

(2) Hook Quarry, West Hoathly (355313). Six tons of conglomeratewere obtained. This locality is referred to by Milner (1923,288). (Thequarries in West Hoathly have attracted geologists for many yearsand the pebble assemblage at Philpots, half-mile north of HookQuarry, has previously been reported (Milner, op. cit.; Kirkaldy,1947).)

The samples were transported to the laboratory by lorry, disaggregated,and pebbles more than one-quarter inch wide screened off. These werewashed and examined under the hand-lens and binocular microscope.Where necessary, investigation was aided by cutting thin sections orpreparing flat surfaces (polished or mounted under glass); several hundred

1 National Grid references lie in the 100 km. square 51 (TQ).

158 P.ALLEN

representative types and all unrecognisable or otherwise interesting pebbleswere treated in this way.

Owing to the absence of large exposures sampling of the Top AshdownPebble Bed (Allen, 1949a, fig. 2) was restricted to small collections from allthe 300+ localities now known . Larger than normal samples were takenfrom two exposures at the extreme NW. and SE. limits of outcrop :

(I) N ear The Grove, Penshurst (513429). Overgrown pit one-quarter miledown the old lane leading to Salman's Farm.

(2) Oxenbridge Hill, Iden (917249). West road-bank by B2082, three­fifths of a mile south-east of bridge over River Rother.

More detailed information is therefore available from these. Laboratorytreatment was as before.

Comprehensive close sampling of the remaining pebble beds has so farproved impossible. Only the Telham and Cliff End Pebble (Bone-) Bedswill be specificallymentioned here (see, e.g. Allen, 1949b, fig. 45; 1960, 11).The former caps the Hog Hills Sands within the Wadhurst Clay, andtherefore intervenes between the Ashdown and Lower Tunbridge Wellshorizons. As will be seen, neither seems to have much bearing on theproblems of the London Uplands.

(b) Petrographic Types and Frequencies

All horizons show an overwhelming predominance c-99%) of siliceouspebbles containing more than 95% silica. This suggests derivation frompre-existing sediments, combined perhaps with intense or prolongedweathering and transport.

A general idea of the relative frequencies of the broad petrographic typesnormally present in the Top Lower Tunbridge Wells Pebble Bed wasgained by analysing the three hundredweight Paxhill sample. This wasfirst well mixed, split down to 2052 pebbles, and the frequencies determinedby counting (see Table I). The values obtained, of course, are in no wayestimates of the average frequencies characterising the pebble bed over itswhole area. Marked fluctuat ions take place from one locality to another.This is sometimes seen even when there is no change in particle size: atHook Quarry (West Hoathly), for instance, there are appreciably morephosphorites than at Paxhill. However, actual changes in the coarsenessof the pebble grade are the most important causes of lateral fluctuationin composition. Phosphorite, chert and red-stained materials becomecommoner as pebble size increases. This is true both between and withinlocalities, and even within single samples. Such behaviour reminds oneof the 'restricted minerals' in the Wealden sand grades (Allen, 1949a).Clearly larger pebbles of phosphorite, chert and red-stained rock were inmore plentiful supply at the sites of deposition than smaller ones.

JURASSIC PEBBLES IN THE HASTINGS BEDS 159

Conspicuously red-stained pebbles form 4.5% of the total: in theassemblage larger than half-inch the ratio is 10.5%. These are minimumfigures, for many which were unstained on their surfaces are found topossess red cores. Yet others have been completely leached of their oxidestains. Since the various stages of leaching occur jumbled together, thecause was probably not entirely a pre-Wealden one.

All the pebbles obtained from the older Top Ashdown Pebble Bedbelong to petrographic types known in the Lower Tunbridge Wellshorizon, excepting the green 'chert' which has not been found. Theytoo were derived chiefly from Upper Jurassic, Lower Carboniferous andOld Red Sandstone formations. Even the more bizarre curiosities ofunknown origin (e.g, orthoclase-quartz-schist) are as widely spreadsouth-eastwards as the outcrops allow. The main differences from theyounger horizon lie rather in changed frequencies: differences, of course,very difficult to assess in view ofthe considerable compositional fluctuationswithin each bed. But, whatever the coarseness of the Ashdown samples ortheir geographical positions relative to London and the Tunbridge Wellsoutcrop, they usually show (1) very much less phosphorite and red­stained material, and (2) more (mainly ?Portlandian) chert. In proportion,the phosphorites and reddened pebbles are quite negligible, and indeedoften only noticeable when larger samples than usual are taken. Oneexplanation among several is that, during the Ashdown-Grinstead interval,erosion redistributed the Upper Jurassic and widened the Old Red outcrops.

Compositional fluctuations within the top Ashdown pebble grades aredifficult to handle, and it is obvious that the figures previously published(Allen, 1949a, 272) do not represent the complete picture. They would inany case be misleading if applied without qualification to problems of theLondon Uplands, for the Top Ashdown Pebble Bed is at least a two-inflowconglomerate (op. cit.). Thus quartz- and quartzite-rich detritus from the'north-eastern river', deficient in chert and very reminiscent of that over theKentish Coalfield (op. cit., 299), becomes an important constituent in thesouth-eastern Weald around Wittersham, Iden, Rye and Hastings. Moreuseful as general guides are analyses of the two random samples cited (seeTable I): one from Iden at the south-eastern extremity of outcrop; onefrom Penshurst, in the north-west, twenty-seven miles nearer the LondonUplands and lying at roughly the same distance from them as the EastGrinstead-Paxhill tract. The latter, of course, was almost entirely underthe aegis of the Uplands. As expected, cherts (particularly the non­Carboniferous ?Portlandian varieties) and red-stained materials are morecommon in the north-west, and quartz and quartzite are cor.respondinglymore abundant in the south-east.

The Cliff End and Telham Pebble (Bone-) Beds are quite different.Quartzes and metamorphic quartzites dominate the exotic pebble suites

160 P.ALLEN

and the few phosphorites doubtfully assigned an origin outside the basinare petrographically distinct. Indeed, both horizons contain abundantpebbles brought in by the 'north-eastern river', which in the same district'pollutes' the Ashdown pebble bed (see above). Severely restricted to the

TABLE IPebbles > 0.25 ins.

Per Cent

41.0 } 64 } 70 Mostly Old Red28.4 Sandstone. (Some

7.0 + 10 direct from Lower6.0 18 10 Palaeozoic 1)3.0 + +

14.7 18 10(8.0) (+) (20)19.4 9.0 18.258.6 65.5 3025.6 24.1 40

7.8 6.9 23 Mostly Old RedSandstone

1.3 + 36.8 3.4 3

(2.5) (3.4) (+)0.6 0.9 0.6 Unknown0.4 0.0 0.0 Old Red Sandstone0.3 + 1.2§ Upper Jurassic

0.1 0.3 + Old Red Sandstone0.1 + + Carboniferous

(4.5) (1.6) (1.2) (Old Red Sandstone)2052 322 165

Petrographic type

CHERTMiscellaneousBedded, non-ooliticOolitic(Patinated)(Red-stained)1:

QUARTZITEWhite, mottled grey and

whiteMiscellaneousBuffDark (inc!. subgreywacke)Pale siltstoneRed-stained](Quartz-veined)

QUARTZOpaque whiteOpaque grey and brownTranslucentAggregated with Fe-Mg

mineralsRed-stainedj(Sheared or lineated)

ORTHOCLASE-QUARTZ-SCHISTGREEN 'CHERT'PHOSPHORITEACID LAVAS, etc. (red­

stainedjtSILICIFIED WOOD(RED-STAINED)

Total pebbles counted

TLTWPB*Paxhill

(356272)

59.572.518.5

9.0(59.1)

(0.49)19.6

TAPBt OriginPenshurst Iden(513429) (917249)

86.3 73.9 }76.6 75.5 U J .16.9 23.8 pper uraSSIC

6 5 0 8 and Lower(22:3) (23:8) Carboniferous

(0.7) (0.0)3.4 6.0

• TLTWPB ~ Top Lower Tunbridge Wells Pebble Bed.t TAPB ~ Top Ashdown Pebble Bed.:j:Percentages for red-stained pebbles are likely to be underestimates.§ Overestimate for this locality.

N.B. I. Types of pebble listed as + are present in the locality. but did not appear in the samplecounted.

2. The top Lower Tunbridge Wells sample was much coarser-grained than the two from thetop Ashdown.

JURASSIC PEBBLES IN THE HASTINGS BEDS 161

south-eastern Weald (Allen, 1949b, fig. 45), the Te1ham bed clearly showsthat it was merely a gravelly patch on a receding strand-line, locallypebbly because it happened there to be retreating across a major deltaicpass of the north-eastern river. Isolated geographically and sedimentologi­cally from the northern streams, their composition can have little bearingon the constitution of the London Uplands.

3. JURASSIC PEBBLES

(a) Top Lower Tunbridge Wells Pebble Bed

(i) Phosphorite. Despite their low proportions (normally less than 1%)many thousand phosphorite pebbles were examined, chiefly from theexposures at West Hoathly (Hook and Philpots quarries) and Paxhill.Generally speaking, phosphorites are most abundant where the pebblesuites are coarsest (particularly Hook Quarry), and virtually confinedtherefore to the degraded north-south distributary (Allen, 1954, text-fig. 1;1959). The vast majority are dark in colour (nearly black), well rolled, andconsist of almost pure collophane. Often the paler nodules demonstrablyowe their colour to recent leaching by soil waters (e.g. Paxhill). Gradationsto phosphatic siltstone and sandstone occur, though rarely. Impregnationwith glauconite is common.

The main types yielding clues to age are rolled fragments of internalcasts ofammonites, a small proportion of which occur at all three localities.The six-ton sample from Hook Quarry yielded 1485such fragments, 224 ofwhich were submitted to Dr. W. J. Arkell. As will be seen from his report(see Appendix), all but two are parts of perisphinctids, representing aPavlovia fauna of the rotunda Zone of the Upper Kimeridge Clay (83­S2261) . Very probably they embrace the entire known ammonite fauna(five species of Pavlovia) of the Upper Lydite Beds. Two internal casts ofcamerae from Paxhill (Sl, S2) were reported by Dr. Arkell as indeterminate,and since then several specimens of Pavlovia (S 3001-6) have been obtainedfrom Philpots (355322).

The preservation of the derived ammonites in the lydite beds and theircorrelative phosphatic nodule beds is identical with that of the Wealdenmaterial, but the fragments are less rolled. Some years ago the siliceouspebble suite of the earlier (Ashdown) horizon suggested comparison withthe lydite beds, carrying the implication that these might be present on thesouth side of the London Platform (Allen, 1949a, 272). In 1957 theGeological Survey's deep boring near Warlingham (Surrey) penetrated anine-inch bed of phosphatised Pavloviae, lying at or very near the top of theKimeridge Clay (maximum possible distance from the Portland-Kimeridge

1 Reading University Geology Department registered numbers.

PROC. GEOL. ASSOC., YOLo 71, PART 2, 1960 11

162 P.ALLEN

boundary: ten and a quarter feet).l The ammonites are preserved as darkphosphorite and, as expected, are less rolled.

Like the Upper Kimeridge phosphatic nodule beds in Dorset (Arkell,1947,82), but unlike the lydite beds of Buckinghamshire, Oxfordshire andWiltshire, the Surrey horizon contains no siliceous pebbles. They may ofcourse enter farther north. Obviously, therefore, the Lower TunbridgeWells cherts, quartzites, etc., could have come either directly from pre­Jurassic outcrops on the London Uplands or secondarily (with the am­monites) through the Upper Kimeridge. The former possibility seems themore likely, in which case the ancient rocks were probably separated inplaces from the overstepping lydite beds by thin Oxfordian, for one ofthe non-perisphinctid fragments (S226) is identified by Dr. Arkell as? Kosmoceras (Lobokosmokeras). The other non-perisphinctid (S225)remains unidentified.

Among the few pelecypod fragments obtained from Hook and PhilpotsQuarries Dr. L. R. Cox has identified Grammatodon sp. (S227-S230) andIsocyprina ?sp. (S231). Though not diagnostic of the Kimeridgian couldquite possibly be of this age.

Equally rare gastropod fragments from Hook include two identified byDr. Cox as Amberleya ?sp. (S237and S238). These resemble the Corallianspecies usually identified as Littorina muricata (J. Sow.).

Highly rolled pebbles with no semblance of organic shape constitutemost of the phosphorite suite and grade imperceptibly into those ofrecognisable molluscan form. Like the molluscan casts they are normallyalmost devoid of detrital matter, but sometimes contain shell chips (e.g.S253 and S254) to fine phosphatic glauconitic sandstones (S255).ProfessorAlan Wood reports that only the long-ranged foraminiferan genusGlomospira is identifiable (S253, from Paxhill), and Dr. R. H. Cummingsinclines to the view that the specimen in question is not Upper Palaeozoic.The same applies to another (unidentifiable) foraminifer from Paxhill(S254), which Dr. Cummings considers unlikely to be Upper Palaeozoicand Professor Wood places as more probably Mesozoic than Palaeozoic.

(ii) Cherts. Unstained (not red) cherts, mostly replacing limestones ofalmost every conceivable kind, commonly form at least half of the largepebbles more than one-quarter inch wide. The non-Carboniferous types areusually unfossiliferous, brittle and black, or else patinated to a soft 'whitechalky looking stuff' (Topley, 1875, 84). As originally suggested by Topleyand confirmed by Relf (1916, 300) and Milner (1923, 298), they may bePortlandian in age, and their petrography is consistent with this. Ooliths, ifpresent, frequently patinate before the matrix, showing up as white 'flour'­filled pock-marks on a dark ground. The dark brittle and soft floury cherts

1 Information communicated by the Director, Geological Survey of Great Britain, and publishedwith his permission.

JURASSIC PEBBLES IN THE HASTINGS BEDS 163

at Paxhill have yielded fragments of a silicified terebratulid (S256); alsocrinoid stems (S258) compared by Dr. L. Bairstow with Balanocrinus, agenus ranging from Trias to Eocene. These pebbles are almost certainlyJurassic. There is little possibility of confusing Jurassic with LowerCarboniferous chert: the pebbles of the latter are brown-mottled, grey, orwhite in colour, less brittle, more rounded , and tough and hard even whenpatinated. If ooliths are present in the Carboniferous cherts, then theyeither wear flush with the surface or stand out in relief.

(iii) Limestone. Milner (1923, 288, 298) records pebbles of oolit ic lime­stone from the East Grinstead district and figures a thin section of onefrom Philpots Quarry (pl. 2IA). By implication he suggests a Portlandianage for it on petrological grounds (p. 298).

(b) Top Ashdown Pebble Bed

Mention has been made of an earlier comparison (Allen, 1949a, 272)between this and the Upper Lydite Bed pebble suite, drawn prior to thediscovery of derived Pavlovids in the Hastings strata.

(i) Phosphorite. This material is much rarer than in the Top LowerTunbridge Wells horizon. Consequently, owing to the impossibility ofcollecting bulk samples, far less is known about it and none of the forms isidentifiable. The petrography is identical with that in the higher bed (e.g.S259), showing frequent glauconite impregnation and the same variationsfrom pure collophane to argillaceous and sandy phosphorite. Almostcertainly the pebbles came from a similar Upper Jurassic source.

(ii) Chert . Pebbles of chert, distinct from their Lower Carboniferousassociates, often patinating to soft white 'flour' and petrographicallyidentical with those of presumed Portlandian age in the Tunbridge Wellsbed, are locally abundant. Normal1y indeed they are commoner thanat the higher horizon. One petrographic variety (S26O) from HoathlyFarm, Lamberhurst (656367), has, unlike its Lower Tunbridge Wellscounterparts, yielded a possible foraminifer, compared by Mr . A. G. Davisto Agathammina and considered by Professor Alan Wood and Dr . R. H .Cummings as more likely non-Carboniferous than Carboniferous.

Several pebbles of monaxon spicular chert from Hurst Green (722287),though probably Lower Carboniferous on general grounds, are extra­ordinarily similar to certain Purbeckian sponge-cherts. This recal1s therecord of a chert pebble with Spongilia purbeckensis in it from the LowerGreensand of West MaIling (Kirkaldy, 1947, 235). The problem will bediscussed more fully in a later paper dealing with the Lower Carboniferouscherts.

3. CONCLUSIONS

Upper Jurassic strata about the level of the lydite beds (Upper Kimeridgeto basal Portlandian) outcropped extensively in the London catchment of

164 P.ALLEN

the 'northern river'. Cherty ?Portlandian limestones higher in the sequencewere probably also exposed. Outcrops of older Upper Jurassic formationswere negligible and there is no indication of Middle or Lower Jurassic.Owing to solution, attrition and winnowing (see also Arkell, below, p. 165)of the pebbles, the relative sizes of the outcrops at anyone time cannot beestimated.

The Upper Kimeridge-basal Portlandian pebbles gradually peter outsouth-eastwards across the Weald. The distant 'north-eastern river' wasvirtually devoid of them, though apparently carrying glauconitic sand ofPortland origin (Allen, 1954). This suggests unconformable blanketing ofthe Kimeridge outcrops eastwards by overstepping Wealden, as alreadyinferred on general grounds (op. cit., text-figs. 1, 2).

Though the relative areas of the Upper Jurassic outcrops cannot bedetermined, evidence strongly suggests important changes during theAshdown-Grinstead interval. By top Tunbridge Wells times the lyditebeds' outcrops seem to have expanded considerably and those of the higherPortlandian to have decreased. This is consistent with the creation andsoutherly retreat of a Portland scarp and the destruction of flatter outliersnorth of it. General considerations indicate concomitant extension ofthe Upper Palaeozoics, a subject to be treated more fully later. Thesechanges, of course, represent the beginning of a denudational sequencefinally resulting in the transport southwards of much Oxford Clay as wellas Palaeozoic detritus by Lower Greensand times (Arkell, 1939; Kirkaldy,1947).

Intense leaching affected certain soils in the Uplands, probably over OldRed Sandstone outcrops supporting forests of gymnosperms.

ACKNOWLEDGMENTSI wish to express my gratitude to many friends, particularly those cited

above, for pondering so long and reporting so succinctly on the miserableJurassic scraps now described. Thanks for assistance are also due to theGeological Survey of Great Britain and numerous landowners, and to theResearch Board of Reading University who helped to defray the cost ofpurchasing the largest 'samples' and transporting them by lorry and car toReading.

REFERENCESALLEN, P. I949a. Wealden Petrology: The Top Ashdown Pebble Bed and the Top

Ashdown Sandstone. Quart. J. geol. Soc. Lond., 104, 257.---. 1949b. Notes on Wealden Bone-Beds. Proc. Geol. Ass., Lond., 60, 275.---. 1954. Geology and Geography of the London-North Sea Uplands in

Wealden Times. Geol. Mag., 91, 498.---. 1959. The Wealden environment: Anglo-Paris basin. Phil. Trans. Roy. Soc.,

242,283.---. 1960. Geology of the Central Weald: Study ofthe Hastings Beds. Geologists'

Association Centenary Guide. No. 16.

D ERI VED J URASSIC AMMONITES 165

ARKELL, W. J. 1939. Derived Ammonites from the Lower Greensand of Surrey andtheir Bearing on the Tectonic Hist ory of the Hog's Back. Proc. Geol. Ass.,Lond., 50, 22.

---. 1947. The Geology of the Country aroun d Weymout h, Swan agc, Corfe andLulworth. M em. geol. Sur v, U.K.

KIRKALDY, J. F. 1947. The Prov enan ce of the Pebble s in the Lower Cretaceou s Rocks.Proc. Geol. Ass., Lond., 58, 223.

MILNER, H . B. 1923. The Geology of the Country around East Gr instead , Sussex.Proc. Geol. Ass. , Lond., 34, 283.

RELF, F. J. 1916. An Invest igat ion of som e Wealden Sands. Geol. Mag ., 3, 295.TOPLEY, W. 1875. The Geology of the Weald. Mem. geol. Surv. U.K.

APPENDIX

Report on Derived Jurassic Ammonites from theTop Lower Tunbridge Wells Pebble Bed

by the late W. J. ARKELL

1. DESCRIPTION, IDENTIFICATIONAND AGE OF THE AMMONITES

224 specimens have been examined (Reading Geology Dept. Reg. Nos.83-8226), obtained by Professor Allen from six tons of the pebble bed, atHook Quarry, West Hoathly, Sussex. Most consist of or show parts ofsmall fragments of internal casts of ammonites preserved in hard blackphosphate, extremely rolled, mostly with a polished surface. The averagesize of the fragments is perhaps IOmm. Few exceed 25 mm. in diameter.The largest [S72] is nearly half a whorl, 49 mm. long, but also very wornand polished. Most consist of intern al casts of one or two camerae or partsof a camera .

The overwhelming majority represent an undoubtedly Upper Jura ssicPerisphinctid fauna . Only two specimens [S225, S226] of those that candefinitely be recognised as parts of an ammonite can be affirmed, from thewhorl-sections, not to be Perisphinctids.

Although there is not a single specimen which, if standing alone, couldbe safely named, the assemblage considered as a whole is unequi vocal andcan be stated with certainty to represent the winnowings of a fauna of Pav­/oviae from the rotunda Zone of the Upper Kimeridge Clay.

Comparison has been made with 114 much better preserved smallderived Pav/oviae, belonging to at least six recognisable species, from theLower Greensand of Wicken, Upware, Potton and Brickhill, in the Sedg­wick Museum (Keeping, 1883). The combination of rolled and unrolledand partly rolled specimens pro vides the requisite standard for comparisonwith the wholly rolled Wealden fragments. Every Perisphinct id fragmentin the Wealden collection is consistent , so far as it goes, with the characters