FOSSIL REPTILES. 175 



to give a sketch of their osteology. Without this, the reader 

 would but imperfectly understand the account which we have 

 to furnish concerning the fossil debris. If we did not do this 

 to the same extent in the case of the mammifera, it was 

 because their species and osteology are now in general better 

 known. 



The precise determination of species and of their distinctive 

 characters constitutes the first and grand basis on which all 

 the researches of natural history should be founded. The 

 most curious observations, and the newest views, lose nearly 

 almost all their value when deprived of this support. Nor should 

 the dryness of this sort of labour prevent those who are de- 

 sirous of arriving at satisfactory results from undertaking it. 



For a considerable period of time, the larger animals were 

 precisely those concerning whose species naturalists were in 

 possession of the least accurate information. Their size, the 

 difficulty of killing, of transporting, of preserving them, and 

 the remoteness of the climates which they inhabit, rendered it 

 impossible to assemble and compare together, at once, a 

 sufficient number of individuals. 



It has been only, for instance, of late years, comparatively 

 speaking, that it became known that many species existed of 

 the elephant and the rhinoceros ; and though it was main- 

 tained more anciently that the species of the crocodiles were 

 numerous, yet so vague and variable were the characters 

 assigned to them, and so little in conformity with truth, that 

 those who maintained the negative of this question could 

 scarcely be blamed. 



The ancients, who might, if they pleased, have compared 

 the crocodile of India with that of the Nile, have entered into 

 no such detail. One author alone, JElian, has casually no- 

 ticed, in a word, the gavialf and the common crocodile of the 

 Ganges. A little more attention was paid by them to the 

 crocodile of Egypt, of which, however, their knowledge was im- 

 perfect enough, though more accurate than their knowledge of 



