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 Ichthyosaurus 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 comparison, illustrating the reciprocal relations of both, and often shewing a real connexion between them, by exhibiting an intermediate 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 considerable 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 communicated 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