566 Mr. De la Beche and Mr. Conybeare on 
the greatest solidity and strength with the least weight of bone, is 
admirably calculated at once to increase the buoyancy of the animal, 
and to enable it to face the waves of an agitated ocean, and has 
doubtlessly been given to it to fit it for its marine abode. 
The general form of the jaw differs from that of the crocodile in 
being much more lengthened and acutely angular ; its termination 
is indeed almost as sharp as the beak of a bird.j: 
The accompanying figures (plate 40, fig. 1 to 10) will explain 
the forms and arrangement of these bones better than any verbal 
description. In order to facilitate comparison with the analogous 
bones in the crocodile, we have employed the same letters with 
which M. Cuvier has marked the head of that animal, in his me- 
moir on the fossil remains of oviparous quadrupeds : + viz. u , den- 
tal ; x y coronoid ; v y angular ; &?, opercular ; y, articular. 
The appearance and range of the dental, coronoid, and angular 
bones on the outer face of the jaw, are shewn in the side view of 
the head (Big. 9. plate 40.) 
The view of the lower jaw, as seen from beneath (fig. 10, plate 
40) exhibits the course of these bones and the opercular through- 
out the jaw. The transverse sections numbered from one to eight 
(plate 40), the position of which is indicated by the dotted lines in 
the side of the head, fully elucidate the form of the several bones 
adapted for strength, being partly squamous and partly dovetailed, so that one bone is 
partly inserted into the other by a sort of angular process, on either side of which they 
overlap each other reciprocally. On these points we propose, in a future communication, 
to speak more in detail. 
J Specimens exhibiting the termination of the jaw in an unmutilated condition are very 
rare; we are indebted to the kindness of Mr. Miller for one which displays that of both 
jaws in a perfect manner. 
f Recherches sur les ossemens fossiles, tome 4. 
