1873.] DR. J. E. GRAY ON THE TRIONYCHIDiE. 43 





Front of the alveolar surface of the lower jaw deeply concave, 

 with a narrow sharp edge, wider and concave behind ; front 

 groove of palate wide, shallow, narrower behind. The nose of 

 the skull is conical, shorter than the diameter of the orbit. 



5. Landemania. Back convex, with a groove on each side of the 



vertebral line ; skull elongate ; lower jaw suddenly contracted 

 in front. 



6. Ida. Back keeled; skull short; lower jaw gradually ta- 



pering. 



7. Dogania. Back flat, scarcely raised ; skull elongate ; lower 



jaw gradually attenuated. 



*** The central palatine groove in front of the internal nostrils 

 broad, shallow, rather wider than, and forminy a margin to, 

 the sides of the internal nostrils. 



8. Platypeltis. The alveolar surface of the lower jaw concave, 



with a sharp raised outer edge, much wider in front ; hinder 

 bones of the sternum with well-developed callosities. 



9. Callinia. The alveolar surface of the lower jaw narrow, 



sharp-edged ; front of lower jaw shelving on the inner side, 

 erect on the sides. 



10. Amyda. 



1 1. Tyrse. The central palatine groove in front of the internal 

 nostrils broad, shallow, much wider than, and enclosing 

 them ; nose elongate. 



1. FORDIA. 



Skull very solid, rather broad, rounded in front ; nose moderate, 

 flattened on the sides ; distance between the square nose-hole and 

 the orbit about half as much again as the diameter of the latter, 

 which is small ; palate flat ; alveolar surface very broad through the 

 whole of its length, with a very narrow slightly impressed groove 

 from the front edge to the septum between the internal nostrils, 

 which are on a line with the front edge of the zygomatic cavity ; 

 lower jaw very strong and thick, depressed in front ; alveolar surface 

 broad and flat in front, narrower and deeply concave on the sides, 

 with a slight central longitudinal ridge, and with a slight concavity 

 and one or two small pits on the sides of the middle part. Length of 

 the skull to condyle 4f inches ; width at condyle 3% inches. 



The skull is nearly as large as the skull of the Baikiea received 

 from Western Africa, but is immediately known from it by being 

 more conical in front. 



1. Fordia africana, Gray, P. Z. S. 1869, p. 119 ; Suppl. Cat. 

 Sh. Rept.p. 100. (Fig. 1, p. 44.) 



Tyrse nilotica, var., Gray, P. Z. S. 1864, p. 88. 

 Hub. Upper Nile (Chartum). 



