64 DR. J. E. GRAY ON THE TRIONYCHID.2E. [Jan. 7, 



Skull elongate ; nose conical ; the distance from the front of the 

 orbit to the aperture of the nostril about half as long again as the 

 diameter of the orbit ; the groove in front of the palate very wide, 

 rather shallow and very much wider behind, so as to include the 

 outside of the internal nostrils. 



In the skull of a smaller specimen brought fiom the Euphrates by 

 Capt. Chesney, the length of the space from the front of the orbit 

 to the aperture of the nostril is much less, not longer than the aper- 

 ture of the orbit, which is larger for the size of the skull than in the 

 larger Egyptian specimens. 



2. Tyrse nilotica. 



Head and limbs and shield covered with equal round white spots ; 

 chin and throat with larger white spots ; beneath white. 



Testudo triunguis, Forskal. 



Trionyx cegyptiacus, Geoffroy, Ann. Mus. iv. p. 7, tab. (animal, 

 good) ; Egypt, i. p. 1 1 6, t. 1 . 



Gymriopus cegyptiacus, Dum. et Bibr., Erp. Ge'n. ii. p. 484. 



Trionyx niloticus, Gray, Syn. Rept. p. 46 ; Cat. Sh. Rept. p. 68, 

 t.42. f. 2 (skull). 



Tyrse nilotica, Gray, Cat. Tort. B. M. p. 48; Suppl. Cat. Sh. Rept. 

 p. 108. 



Trionyx labiatus, Bell, Test. tab. (with skeleton). 



Aspidonectes aspilus, Cope, Proc. Acad. Nat. Sci. Philad. 1859, 

 p. 205 (adult). 



Sab. River Nile. 



B. Dorsal disk with a broad transverse odd bone in front, which is 

 united to the rest of the disk by a straight suture in the adult ; 

 lateral bones of the sternum expanded, and covered with well- 

 developed callosities on the whole surface ; posterior pair of 

 bones slender, not dilated, without callosities. 



Rafetus. 



Rafetus, Grav, P. Z. S. 1864, p. 81 ; Suppl. Cat. Sh. Rept. i. 

 p. 103. 



Skull broad, depressed ; nose rounded ; nose-cavity square, large ; 

 space between the nose and the orbits one third the diameter of the 

 latter ; palate rather concave ; alveolar surface narrow in front, wider, 

 and with an internal ridge on the sides behind ; the groove in front 

 of the palate very wide, rather deep, wider and deeper behind, rather 

 wider than the front edge of the large internal nostrils, and forming 

 a narrow margin to the outer sides of them. Lower jaw with a slightly 

 convex chin ; alveolar surface rather broader in front than on the 

 sides, slightly concave, with a very indistinct central longitudinal line 

 exceeding the whole width of the surface ; hinder part of the sides 

 narrower, with a longitudinal concavity, and with an elevated inner 

 and more elevated outer edge. Length to occiput 3£ inches ; dia- 

 meter at the front of the temple 2 inches. 



The lateral bones of the sternum are entirely covered with callo- 



