Dr. J. E. Gray on the Family Chelydradse. 67 



long and bowed out on the sides, with a much longer central 

 cavity than I have observed in the Chelonians. 



Section I. Crucisterna, Gray, Hand-list of Sh. Rept. p. 56. 



The sternum cross-shaped, simple and acute behind, with 

 more or less elongate lateral processes to the sternal costal 

 suture, and united to the marginal bones by an osseous suture. 

 The anterior pair of bones elongate, broad, with a well-de- 

 veloped odd internal bone; the two middle pairs are well 

 developed, and, in the adult, united on each side by a straight 

 dentate suture, and also by a medio-longitudinal suture. The 

 hinder pair of bones are slender and united together in the 

 middle, and in front to the hinder edge of the central pair of 

 bones. 



In the young animal the pair of lateral bones are not united 

 by a longitudinal central suture, and there is a triangular 

 cavity on the hinder sides of the odd central bone and at the 

 front end of the lateral bone ; but these bones increase in 

 breadth, and more or less approach together, and are united 

 by a linear suture. 



These terrapins are furnished with two beards ; one species, 

 however, described as coming from Guatemala, has a second pair 

 of beards ; but this may be accidental in the specimen, as I do 

 not recollect it to have occurred in any other water-tortoise ; 

 at least it wants confirmation. 



Tribe I. Chelydraina. 

 The sternum with five pairs of shields ; tail elongate. 

 1. Macrochelys. 



1. M. Temminckii. 



2. Chelydra. 



1. C. serpentina. Beards 2. 



2. C. Rossif/nonii, Bocourt, t. v. f. 2. Beards 4. 



Tribe II. Staurotypina. 



The sternal shields in four pairs ; the hinder pair on each 

 side sometimes united together into one shield ; and there is 

 sometimes a small central anterior shield, the representative 

 of the anterior angular pair of sternal shields in other terra- 

 pins. 



The anterior pair of bones and the odd bone are broad ; the 

 lateral pair of bones are united all together into one mass by 

 a longitudinal central suture and by a linear transverse sub- 

 central suture. The hinder pair of bones are elongate, united 

 together by a linear longitudinal suture, and to the hinder 



5* 



