AND AVES OF NORTH AMERICA. 



123 



T K S T V D1KA T * . 



CRYPTODIBA. 



EMYDIDAB. 



EMYDINAE. 



STYLEMYS, Leidy. 



Stylemys, Testudo and Emys, Leidy, Proceed. Ac. N. Sci., 1851, 172. Testudo, Leidy 1. o. 1852, 59. 

 Contrib. to Knowl., 1852, 103. 



Sivutlison. 



The species which I icier to this genus, are Emydoids with the usual elongate form 

 of digits which characterizes the aquatic species, but with a single caudal marginal scutum, 

 as in Testudo. Another Emydoid genus which approaches Testudo most, is Manuria, 

 Gray. Here however the anal marginal plate is divided, and the pectoral plates do not 

 meet on the median line. In Stylemys the latter are only narrowed. 



The ilium is formed much as in Chclydra, somewhat dilated proximally in a posterior 

 direction. The pubis is like some Emydoids in the length and lateral direction of its 

 lateral process, while its stout form, with distal dilatation, articulated with its fellow on 

 the median line is like that of Chclydra. 



A right femur is entirely Testudinoid, and presents one peculiarity which I have only 

 observed in Testudo polyphemus. The great trochanter (which is always large in the 

 Testudinata) extends entirely round from its origin, to near the head of the lemur, em- 

 bracing a marked fossa. In other genera the greater tuberosity with the lesser enclose a 

 fossa-like groove, which separates them entirely. 



The capitula of the ribs extend to the vertebra, but not to their centra ; they are in 

 contact with the laminiform neural spines. 



A marked character of the genus also consists in the considerable separation of the 

 neural arch from the vertebral carapacial bones. It is suspended as it were, some distance 

 below them by the laminiform elevation of the joined neurapophyses, which are united by 

 suture to the similar thin plate-like neural spines, which descend from the transverse 

 vertebral expansions. The depth of tins vertebral septum is greater than the length of 

 each vertebral bone, behind the middle of the column. The centra are very thin as in 

 Cistudo. 



Leidy named some individuals of one of the species, Stylemys, while others were 

 referred to Emys. As he gave no characters to it, and afterwards abandoned it, referring 

 the species to Testudo, I only adopt the name for the purpose of diminishing the synonymy. 



