258 HISTORICAL PALEONTOLOGY. 



water? Such an idea was at one time entertained, in conse- 

 quence of the biconcave character of the caudal vertebrae, and 

 it is often suggested by the mere magnitude of the creature, 

 which would seem to have an easier life while floating in water, 

 than when painfully lifting its huge bulk, and moving with 

 slow steps along the ground. But neither of these arguments 

 is valid. The ancient earth was trodden by larger quadrupeds 

 than our elephant; and the biconcave character of vertebrae, 

 which is not uniform along the column in Cetiosaurus, is per- 

 haps as much a character of geological period as of a me- 

 chanical function of life. Good evidence of continual life in 

 water is yielded in the case of Ichthyosaurus and other Ena- 

 liosaurs, by the articulating surfaces of their limb-bones, for 

 these, all of them, to the last phalanx, have that slight and 

 indefinite adjustment of the bones, with much intervening 

 cartilage, which fits the leg to be both a flexible and forcible 

 instrument of natation, much superior to the ordinary oar- 

 blade of the boatman. On the contrary, in Cetiosaur, as well 

 as in Megalosaur and Iguanodon, all the articulations are 

 definite, and made so as to correspond to determinate move- 

 ments in particular directions, and these are such as to be 

 suited for walking. In particular, the femur, by its head pro- 

 jecting freely from the acetabulum, seems to claim a movement 

 of free stepping more parallel to the line of the body, and 

 more approaching to the vertical than the sprawling gait of 

 the crocodile. The large claws concur in this indication of 

 terrestrial habits. But, on the other hand, these characters 

 are not contrary to the belief that the animal may have been 

 amphibious; and the great vertical height of the anterior part 

 of the tail seems to support this explanation, but it does not 

 go further. . . . We have therefore a marsh-loving or 

 river-side animal, dwelling amidst filicine, cycadaceous, and 

 coniferous shrubs and trees full of insects and small mamma- 

 lia. What was its usual diet? If ex ungue leonem, surely ex 

 dente cibum. We have indeed but one tooth, and that small 

 and incomplete. It resembles more the tooth of Iguanodon 

 than that of any other reptile; for this reason it seems prob- 

 able that the animal was nourished by similar vegetable food 

 which abounded in the vicinity, and was not obliged to con- 

 tend with Megalosaurus for a scanty supply of more stimu- 

 lating diet. " 



All the groups of Jurassic Reptiles which we have hitherto 

 been considering are wholly unrepresented at the present day, 



