164 G. A. LEBOUR ON DEPOSITS FORMUW IN BRITISH SEAS.

deposition of the more bulky and heavier grains of sand. Everypatch of mud or clay the ingredients of which have been broughtfrom a distance must to a certain extent be a centre of calm. Thepoints of the greatest rapidity and violence of current action areshown by the bare rock patches; while the intermediate stages ofagitation are represented by the other deposits, ranging from muddysand, sand, sandy gravel, etc., to the coarsest shingle beds.Where, as in the North Sea, for example, the loose material ofthe sea-bottom is to a great extent homogeneous, the calm-spotswill be marked by features only, and are therefore less noticeable.

2. NOTES ON SPECIMENS OF PHOSPHORITE FROM THE DEPARTMENT

OF THE LOT, FRANCE.

By F. W. RUDLER, ESQ., F.G.S., M.A.I., &c.

In bringing before the Association some fine specimens ofphosphorite which have recently been brought to this country fromBach, in the Department of the Lot, and have been kindly placedin my hands by Mr. Walter Pearce, it may not be out of place tooffer some remarks on the conditions under which the mineraloccurs in this locality. The discovery of phosphorite in the Southof France dates back to 1865, when a chemist named M. J. A.Poumarede, having returned from Mexico and settled near Caylus,in the Department of Tarn-et-Garonne, was struck with the appear­ance of certain nodular bodies which were abundantly scatteredover the surface of the Oolitic limestone in his neighbourhood.On submitting some of these nodules to analysis he found thatthey were not carbonate, but phosphate of calcium. Although M.Poumarede was fully alive to the value of his discovery, he failedto follow it up at the time, and was soon afterwards removedby death. Attention, however, was seriously directed to theseminerals on the conclusion of the Franco-German war j and since1871 they have been actively worked in a large number of localitiesin the Departments of the Lot, Aveyron, and Tarn-et-Garonne.

The phosphorite. occurs partly in regular veins running throughthe limestone, and partly in "pockets" or irregular deposits incavities which, in some cases, reach a width of more than 100 feet.It will be seen from the specimens exhibited that the mineral

F. W. RUDLER ON SPECIMENS OF PHOSPHORITE FROM: ~·RA"l(CE. 165

frequently assumes nodular forms, with a beautifully concentricstructure resembling that of B regularly formed agate; whilstother specimens show a finely banded structure, such as would bepresented by a mineral deposited from solution in successivelayers on the walls of a fissure. According to several analysesby M. Bobierre, the French pbosphorite contains on an averageabout 36 per cent. of phosphoric anhydride, corresponding to 78per cent. of tricalcic phosphate. It also contains chlorine andfluorine, and it is notable that, as in the Bavarian and Nassauphosphates, iodine is present, presumably as iodide of potassium.The geological age of these phosphatic deposits may be inferredfrom the associated organic remains. Some of these fossils arenow exhibited. The working of the French phosphorite has,indeed, brought to light II remarkable assemblage of mammalianremains, similar, in many respects, to those from the gypseousdeposits of the Paris Basin. In addition, however, to theoccurrence of Anoplotherium; Palaotherium, Dichobun e, and otherwell-known genera, the deposits have yielded some new fossilsallied to the lemurs, or Madagascar monkeys. One of these, fromQuercy, has, been described by M. Filhol, under the name ofNecrol emur antiquus, whilst another new genus has been estab­lished by M. Delfortrie on some remains from Bedner. It has,however, been asserted by M. Filhol that the Bedner fossil,which had received the name of Palceolemur Betillei, is not a truelemur, but is even more interesting since it presents characterswhich bring it into relation with the lemurs on the one hand andwith the pachyderms on the other. Those who wish to studythe occurrence of the French phosphatic deposits and the organicremains which they have yielded may be referred to the recentwritings of MM. Daubree, Delfortrie, Durand-Clay, Filhol, Gervais,Leym erie, and Malinowski.

3. A PROBABLE ORIGIN OF TIlE PERFORATIONS IN SHARKS'

TEETH FROM rua CRAG.

By H. A. BURROWS, ESQ.

As there exists in recent specimens a foramen for the passageof blood-vessels for the nutrition of the pulp filling the interior ofthe tooth, and opposite to this numerous small holes on the other