“The cave of Cro-Magnon is formed by a projecting ledge of cretaceous limestone (rich with fossil corals and polyzoans), having a thickness of 8 metres and a length of 17 metres (Fig. 72, P). The bed which it overlies, and the destruction of which has given rise to the cave, abounds with _Rhynchonella vespertilio_, which is a type fossil, fixing the geological horizon. The débris of this marly and micaceous limestone had accumulated on the original floor of the cavern to a great thickness, at least for 0·70 metres (see Fig. 72, A), when the hunters of the reindeer stopped here for the first time, leaving as a trace of their short stay a blackish layer (Fig. 72, B), from 0·05 to 0·15 metre thick, containing worked flints, bits of charcoal, broken or calcined bones, and in its upper portion the elephant tusk before alluded to (Fig. 72, _a_). [Illustration: FIG. 72.--Detailed Section of the Cave of Cro-Magnon, near Les Eyzies. Scale = 1/100 (1 centimetre to 1 metre). A Débris of soft limestone. B First layer of ashes, &c. C Calcareous débris. D Second layer of ashes, &c. E Calcareous débris, reddened by fire under the next layer of ashes, &c. F Third layer of ashes, &c. G Red earth, with bones, &c. H Thickest layer of ashes, bones, &c. I Yellowish earth, with bones, flints, &c. J Thin bed of hearth-stuff. K Calcareous débris. L Rubbish of the Talus. N Crack in the projecting ledge of rock. P Projecting shelf of hard limestone. Y Place of the pillar made to support the roof. _a_ Tusk of an elephant. _b_ Bones of an old man. _c_ Block of gneiss. _d_ Human bones. _e_ Slabs of stone fallen from the roof at different times. ]