THEORY OF THE EARTH. &7 



general causes, and that the careful investigation 

 of it affords one of the best means for discovering 

 and explaining the nature of these causes. 



27. Of the Difficulty of distinguishing the Fossil 

 Bones of Quadrupeds. 



thp study of the fossil remains of the 

 greater quadrupeds is more satisfactory, by the 

 clear results which it affords, than that of the re- 

 mains of other animals found in a fossil state, it is 

 also complicated with greater and more numerous 

 difficulties. Fossil shells are usually found quite 

 entire, and retaining all the characters requisite 

 for comparing them with the specimens contained 

 in collections of natural history, or represented in 

 the works of naturalists. Even the skeletons of 

 fishes are found more or less entire, so that the 

 general forms of their bodies can, for the most 

 part, be ascertained, and usually, at least, their ge- 

 neric and specific characters are determinable, as 

 these are mostly drawn from their solid parts. In 

 quadrupeds, on the contrary, even when their en- 

 tire skeletons are found, there is great difficulty in 

 discovering their distinguishing characters, as these 

 are chiefly founded upon their hair and colours, 

 and other marks which have disappeared previous 

 to their incrustation. It is also very rare to find 

 any fossil skeletons of quadrupeds in any degree 

 approaching to a comple state, as the strata for the 

 most part only contain separate bones, scattered 



13 



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