DINOSAURIA. 291 



In the proportion of the successional teeth which is formed 

 in the formative cavity in the substance of the jaw, the Mega- 

 losanr offers a closer resemblance to the mammalian class 

 than do any of the recent or extinct crocodilian or lacertian 

 reptiles. But the evidence of uninterrupted and frequent 

 succession of the teeth in the Megalosaur is unequivocal ; 

 and this part of the dental economy of the great carnivorous 

 reptile is strictly analogous to that which governs the same 

 system in the existing members of the class. The different 

 forms of the teeth at different stages of protrusion did not fail 

 to attract the attention of the gifted discoverer of the great 

 predatory saurian, in whose words this notice of its dentition 

 may be fitly concluded : — 



" In the structure of these teeth we find a combination of 

 mechanical contrivances analogous to those which are adopted 

 in the construction of the knife, the sabre, and the saw. When 

 first protruded above the gum, the apex of each tooth presented 

 a double cutting edge of serrated enamel. In this stage its 

 position and line of action were nearly vertical ; and its form, 

 like that of the two-edged point of a sabre, cutting equally on 

 each side. As the tooth advanced in growth, it became curved 

 backwards in the form of a pruning-knife, and the edge of 

 serrated enamel was continued downwards to the base of the 

 inner and cutting side of the tooth, whilst on the outer side a 

 similar edge descended, but a short distance from the point ; 

 and the convex portion of the tooth became blunt and thick, 

 as the back of a knife is made thick for the purpose of pro- 

 ducing strength. The strength of the tooth was further in- 

 creased by the expansion of its side. Had the serrature 

 continued along the whole of the blunt and convex portion of 

 the tooth, it would in this position have possessed no useful 

 cutting power ; it ceased precisely at the point beyond which 

 it could no longer be effective. In a tooth thus formed for 

 cutting along its concave edge, each movement of the jaw 



