302 Dr. J. E. Gray on Chelonians. 



costal plates tubercular. Head and back of neck brown ; lower 

 side of throat pale. 



* The second vertebral plate simple, and narrower than the first 

 vertebral plate. 



1. Hydromedusa Maximiliana. B.M. 



The front vertebral plate oblong, transverse, broad, and 

 angularly bent at the sides ; the second vertebral plate four- 

 sided, longer than broad, simple at the front lateral angles, and 

 scarcely broader than the hinder end ; tlie hinder vertebral 

 and costal plates with a prominent tubercle on the hinder edge. 

 Front pair of marginal plates very large, four-sided, twice as 

 broad as long. Sternum deeply concave behind. The intergular 

 plate large and broad ; the angular part behind not so long as 

 the front square part. 



Hah. Brazil. 



The second marginal plate on each side large, broad, pent- 

 agonal, the inner side being, like the ninth marginal plate, 

 biangular on the inner side. Tlie two last vertebral and costal 

 plates tubercular. The sternum, on the suture between the 

 two hinder pairs of plates, very deeply concave. 



** Second vertebral plate with a narrow projecting lobe at the front 

 lateral angles, rather wider than the first vertebral plate. 



2. Hydromedusa platanensis^ Hand-list Sh. Kept. p. 64. B.M. 



Front vertebral plate very short, more than three times as 

 broad as long, transverse, truncated at the ends ; second ver- 

 tebral plate four-sided, longer than broad, with a small pro- 

 jecting lobe at the front lateral angles, which project beyond 

 the edge of the front vertebral plate. Front pair of marginal 

 plates very large, broader than loug. The two hinder vertebral 

 plates with a prominent tubercle on the hinder edge. Sternum 

 flat both before and behind. Intergular plate large and broad, 

 the angular part behind longer than the front square part. 



Hah. Rio de la Plata {Bravard). 



The tubercles on the vertebral and hinder costal plates are 

 not nearly so large as those of H. Maximiliana ; and the last 

 but one of the lateral plates is very broad, the angle in the 

 middle of its inner side very acute, and extending far up 

 along the hinder edge of the last costal. 



The front central bone behind the pelvis square, divided by 

 a suture down the centre ; and the hinder bone between it and 



