a was at one time entertained,
in consequence 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 perhaps as much a character
of a geological period as of a mechanical function of life. Good
evidence of continual life in water is yielded in the case of
Ichthyosaurus and other Enaliosaurs, 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 movements in particular
directions, and these are such as to be suited for walking. In
particular, the femur, by its head projecting 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 mammalia. 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 probable that the animal was
nourished by similar vegetable food which abounded in the vicinity,
and was not obliged to contend with Megalosaurus for a scanty
supply of more stimulating diet."

All the groups of Jurassic Reptiles which we have hither