34 



DINOSAURS. 



length of its skeleton is estimated to have been between 60 and 80 feet. On the 

 other hand, some species were comparatively small, and not more than a couple of 

 feet in length. Although the whole of these reptiles are markedly distinct from 

 the crocodiles, yet they agree with them in the general characters of their 

 skulls, vertebrae, and ribs ; but they differ so decidedly from one another that it is 

 not easy to give a definition of the entire order. They are, indeed, divided into 

 three well-marked groups, with so many differences between them that in the 

 opinion of many they are entitled to rank as separate orders ; and it will, accord- 

 ingly, be most convenient to treat these three groups seriatim. 

 Lizard-Footed The most stupendous members of the order are included in a 



Group. group which may be conveniently designated lizard-footed dinosaurs, 

 on account of their walking in the ordinary lizard-like manner, and in having five 

 toes to the feet. The most striking peculiarity of this group is to be found in the 



LEFT-SIDE VIEW OF AN IMPERFECT VERTEBRA OF A 



lizard-footed dinosaur. (From the Quart. 

 Journ, Geol. Soc, 1893.) 



INNER AND LATERAL VIEWS OF A TOOTH OF 

 A HOPLOSAUR. 



circumstance that the vertebrae of the neck and back, as shown in the accompany- 

 ing figure, had large cavities in their sides, which in the living state may have 

 been filled either with cartilage or with air. These vertebrae resembled those of 

 existing crocodiles, as described on p. 6, in having a ball at one end and a cup at the 

 other ; but whereas in crocodiles the ball is at the hinder end of the body and the 

 cup in front, in these dinosaurs precisely the reverse of this arrangement obtained. 

 As regards their dentition, these reptiles had their teeth implanted in distinct 

 sockets, like crocodiles ; but the teeth themselves, as shown in the accompanying 

 figure, were of a peculiar spatulate shape, with the outer side convex and the inner 

 concave. Agreeing in the general structure of their pelvis with crocodiles, these 



