A FOSSIL JAW FROM STONESFIELD 



hard Jurassic slate, and is one of the most 

 ancient evidences of the existence of a mammal. 

 The sight of its double fangs at once rendered 

 it almost certain that the teeth must be those 

 of a mammal : the whole shape of the jaw is 



Fig. 56. — Photograph of the skull and lower jaw of a true 

 Crocodile. The numerous peg-like teeth of different sizes, 

 firmly implanted in the jaw-bones, are shown. 



like that of a small mammal, such as the hedge- 

 hog. 



We must now take up again the general story 

 of extinct animals ; and to do so we will first of 

 all go back, so to speak, a little way into the 

 strata deposited on the earth's surface— just far 



83 



