398 DR. J. E. GRAY ON THE GENERA OF TURTLES. [Apr. 1, 



triangular, truncated in front, and slightly notched behind in the 

 centre. The hinder pair of caudal plates are very long, much longer 

 than broad, four-sided, the hinder and outer sides shortest ; and the 

 hindermost lateral plate has a straight inner edge, and is not angular 

 and produced as in Eremonia elongata. 



The dorsal shield of this genus has some resemblance to the shield 

 of Eremonia elongata in the large size of the caudal marginal plates; 

 but of the latter genus the head and limbs are unknown : it belongs 

 probably to the family Cuouanidce, as it has five costal shields on 

 each side ; while this has only four, and belongs to Cheloniadce. The 

 shields of the two genera may be thus distinguished : — 



Onychochelys. Eremonia. 



Costal plates 4.4. Costal plates 5 . 5. 



First vertebral shield trian- First vertebral shield hexa- 



gular, with lateral angles trun- gonal, as broad as long, 

 cated, much longer than broad. 



Second, third, and fourth ver- Second, third, and fourth ver- 



tebral shields hexagonal ; lateral tebral shields very long, oblong, 

 angles produced, as broad as four-sided, with the middle of 

 long. the sides rather prominent, much 



longer than broad. 

 Thepenultimatemarginalshield The penultimate marginal shield 

 with a straight inner edge. prominent, angular in the middle, 



projecting between the last costal 

 and the last vertebral shields. 



1. Onychochelys kraussi, Gray, Hand-list, p. 93. (Fig. 1, 

 skull ; fig. 2, animal.) 



Chelonia marmorata, Krauss, not Dumeril and Bibron. 



Hab. Ocean, French Guiana (Krauss). 



The palate deeply concave, with a deep well-marked groove on 

 each side of the basioccipital bone, which has a very strong ridge 

 on its front lateral margin. The alveolar surface of the upper beak 

 with a very high arched ridge, which is much the highest in front, 

 and very rugose on its edge and on the hinder part of its surface, 

 having an obscure indication of a ridge parallel to its hinder mar- 

 gin, and then shelving down to the inner nostrils. The alveolar sur- 

 face of the lower beak concave, very wide in front, narrow on the 

 sides, becoming narrower behind, and with a sharp elevated ridge on 

 the inner margin. There is a longitudinal central ridge across the 

 hinder half of the concavity of the lower alveolar edge. The con- 

 cavity of the alveolar of the lower jaw fits on to the ridge in the upper 

 jaw. The iuner surface of the beak within the hinder ridge is yellow 

 and horny like the outer surface. It is broad and high in front, 

 gradually narrowing on the sides ; the surface is smooth, with a 

 groove on each side in the middle of the front ; and the sides have 

 close paralell grooves ending in crenations on the margin of the ridge. 



The specimen in the British Museum is full-grown, and has the 

 dorsal shell 35 in. long, and 31 in. broad in the widest part over the 



