CHELONIA. 39 



agrees in its general form with that of Chel. subcristata, but is less extensive, as regards 

 its bony surface, than in Chel. loiifflceps or even than in Chd. breoiceps. The entosternal 

 bone (s) is somewhat wedge-shaped, with the anterior margin triangular, and a short 

 winged process on each side of the anterior third of the bone extending outwards and 

 backwards. The posterior extremity of the bone, and the winged processes are 

 dentate. The episternals {es) are aliform, tending backwards and outwards, and 

 inclosing between them the head of the entosternal (*), and the anterior processes of the 

 hyosternal bones [Its). The latter have the anterior processes extending forwards on 

 each side of the entosternal, approximating at their extremity the aliform processes of 

 that bone. The median or internal processes nearly meet on the median line, and the den- 

 tations are deep but slender ; each hyposternal {ps) unites similarly with its fellow, and 

 the posterior process extends backwards, in a long, narrow, triangular piece, uniting with 

 the xiphisternal {xs), which latter forms a very elongated rhomb, the breadth of which 

 is scarcely one fourth of its length, which in the present specimen is no less than two 

 inches six lines. This form, with the elongation and narrowness of the posterior process 

 of the hyposternal, gives to the hinder portion of the plastron in this species a narrower 

 and more elongated outline than we find in almost any other; an approach to 

 which is, however, indicated in the imperfect specimen of Chel. subcristata figured in 

 Plate 15. 



The external notch, between the external process of the hyosternal and hyposternal, 

 is deep and rounded. The central interspace is nearly quadrate, and about half as 

 long again as it is broad. 



Inches. Liues. 



Lengtli of the carapace as far as it is preserved ... 9 5 

 Breadth of ditto from the extremity of the third costal plate on 



one side to that on the other ...... 7 4 



Ditto, following the convexity of the carapace ....!) 3 



Length of plastron from the anterior margin of the episternal 



to the extremity of the xiphisternal .... 8 4 



Breadth of ditto across the hyosternals ..... 7 



The only specimen of this species which I have seen is from Sheppy, and is in the 

 fine collection of J. S. Bowerbank, Esq., F.R.S. 



T. B. 



