68 Dr. J. E. Gray on the Family Chelydradas. 



outer margin of the hinder lateral bones by a simple linear 

 suture. 



The tail of the animal is short ; and the front or hinder lobes 

 of the sternum have been said to be more or less movable ; 

 but they cannot be as they are in the true trap box tortoises, 

 as the sutures between the bones are not the same as the 

 sutures on the plates of the sternum. 



This tribe contains three genera. 



Section I. The sternal plates in four pairs of shields, the hinder 

 pair sometimes united into one plate, without any odd anterior or 

 gular plate. The lateral processes broad, with distinct axillary 

 and inguinal shields. 



1. Staurotypus. Sternum broad, straight on the sides, 

 roundly truncated in front. The front lobe separated from the 

 middle part of the sternum by a well-marked transverse 

 sinuous suture. 



1. S. triporcatus. 



2. Stauremys. Sternum narrow, narrowed in front, con- 

 verging on the sides. The front lobe immovable, without 

 any transverse suture. 



1. S. Salvinn. 



Mr. Cope believes u the genus Staurotypus belongs to the 

 family Kinosternidas, a family defined by the absence of the 

 mesosternal bone ; " but this is a mistake. In the adult speci- 

 men in the Museum, the mesosternal bone is visible both 

 externally through the thin sternal plates and on the inner 

 surface of the sternum. In the adult animal the front lateral 

 pair of bones are very broad, approaching those of Kinostemon 

 in form ; but there is a large, well-developed, subtriangular 

 odd or mesosternal bone between the hinder part of their inner 

 edges. In the adult all these bones are strongly united 

 together by a very narrow, almost obliterated suture. But it 

 appears doubtful to me whether Mr. Cope speaks from having 

 examined a specimen ; at least his account does not lead one to 

 believe that he had. 



Section II. Sternal plates in four pairs, with small odd central or 

 gular plate in front ; lateral processes very narrow ; inguinal 

 shields small or wanting. 



3. Claudius. 



1. C. angustatus, Cope. C. macrocephalus, Boucard. 



Mr. Cope established this genus for the above species, 

 which I only know from Bocourt's figure, and which appears 



