562 Mr. De la Beche and Mr. Conybeare on 
animals appear unquestionably to have lived, principally at least, in 
the sea, and to have received the peculiarities of organisation to 
which we have alluded, in order to fit them for such an habitation, 
the term Enalio-Sauri may be proposed as a classic appellation to 
denote the whole order. Of the genera composing it, the Ichthy- 
osaurus recedes most widely from the forms of the lizard family, 
in order to approach those of fishes ; but it is still incomparably 
nearer to the former ; and a careful study of its osteology presents, 
as will presently be seen, a beautiful series of analogies with that of 
the crocodile, in all the most essential parts. 
The newly discovered animal, named on that account Plesiosaurus, 
approaches much more nearly to the crocodile, forming in its whole 
structure, a link between it and the Ichthyosaurus ; hence it acquires 
a high and peculiar interest, as affording a middle term of com- 
parison, illustrating the reciprocal relations of both, and often 
shewing a real connexion between them, by exhibiting an inter- 
mediate gradation of form in parts, which would, at first sight, 
appear the least likely to be reconciled. 
Of these animals, the Ichthyosaurus has already engaged a con- 
siderable share of attention among the scientific public, having been 
illustrated by a writer whose name stands deservedly high among 
the comparative anatomists of this country. Yet, since the materials 
from which his descriptions were drawn up came only into his 
possession gradually, and were with a praise-worthy readiness com- 
municated instantly to the public, the circumstances of the case 
rendered it impossible to attempt a regular and connected view of 
the whole osteology of this animal, and a series of detached essays 
on such individual points of its structure as the specimens happened 
to present, was all that was practicable ; hence many of the most 
important parts of the skeleton, the whole osteology of the head for 
