36 PROGRESS OF PALAEONTOLOGY u 



are found all over the surface and in the interior 

 of the dry land ; and all calcareous rocks are made 

 up of their remains. Secondly, a great many of 

 these shells which are found in Europe are not 

 now to be met with in the adjacent seas ; and, in 

 the slates and other deep-seated deposits, there 

 are remains of fishes and of plants of which no 

 species now exist in our latitudes, and which are 

 either extinct, or exist only in more northern 

 climates. Thirdly, in Siberia and in other 

 northern regions of Europe and of Asia, bones 

 and teeth of elephants, rhinoceroses, and hippo- 

 potamuses occur in such numbers that these 

 animals must once have lived and multiplied in 

 those regions, although at the present day they 

 are confined to southern climates. The deposits 

 in which these remains are found are superficial, 

 while those which contain shells and other marine 

 remains lie much deeper. Fourthly, tusks and 

 bones of elephants and hippopotamuses are found 

 not only in the northern regions of the old world, 

 but also in those of the new world, although, at 

 present, neither elephants nor hippopotamuses 

 occur in America. Fifthly, in the middle of the 

 continents, in regions most remote from the sea, we 

 find an infinite number of shells, of which the most 

 part belong to animals of those kinds which still 

 exist in southern seas, but of which many others 

 have no living analogues; so that these species 

 appear to be lost, destroyed by some unknown 



