and the changes they undergo in different parts of the jaw, from its anterior to its posterior extremity, and also the manner of their application to each other

Bones of the upper part of the Head

These have the same marked coincidence with those of the crocodile which distinguishes the bones of the lower jaw; they are shewn in the accompanying figures (pi. 40) fig. 9,11, 12, marked by the letters employed by M. Cuvier. Since to describe them at length would be generally to repeat the words of that author, in treating of the structure of that animal (the crocodile), we shall confine ourselves to a rapid sketch, noticing principally the peculiarities of configuration by which the Ichthyosaurus differs from this type, most of which arise from the adaptation of the parts to the narrow and elongated contour of the whole. The eye also is rather lower placed than in the crocodile, the bottom of the orbit being nearly on a level with the line of the opening of the jaws ; this produces some very slight changes in the form of the adjacent bones; and perhaps a still more important deviation occurs in the place of the nostrils; but this point still remains involved in some degree of obscurity.
We shall first consider those bones which appear on the sides and inner part of the mouth, as exhibited in figures 9, 11, and 12, plate 40. and in the transverse section fig. 3, of the same plate.
The general outline of the upper, like that of the lower jaw, is much more pointed than in any species of crocodile ; its termination resembles that of the porpoise, the bones of the opposite sides opening at the end so as to form a narrow angular slit; this slit requires an attentive examination from the doubts that have arisen