destruction of the land which has taken place in the long lapse of ages, to which attention has already been directed in treating of the Meiocene period. In my opinion there have been ossiferous caverns in all geological periods, but they and all shelters then accessible to animals, together with the rocks in which they were hollowed, have been carried away so completely that no traces of any caverns of those times have been discovered in any part of the world. The rain, the alternation of heat and cold, the carbonic acid in the atmosphere, the acids evolved from decaying vegetation, and the breakers on the sea-shore, have wrought this wholesale destruction so thoroughly that there are only two caverns that can be said to be even as old as the mid Pleistocene. In one of these, at Oreston near Plymouth, Mr. Whidbey[1] discovered the remains of the big-nosed rhinoceros in the year 1816. The other is at Baume, in the Jura, in which the remains described by Professors Lartet[2] and Gervais were found, belonging to the machairodus, a non-tichorine rhinoceros, to the ox, wild boar, elephant, spotted hyæna, and cave bear. In both these the mammalia are identical with those of the mid Pleistocene, with the exception of the machairodus, which must, however, have been living at that time, since it occurs in mid and late Pleistocene strata.
