46S 



PROCEEDINGS OF THE ACADEMY OF 



[April, 



Lower Sonoran: 



Ctenosaura 

 Dipsosaurus 

 Crotaphytus 

 ■Sauromalus 

 Callisaurus 

 •Uma 



Holbrookia 

 Uta 



■Sceloporus 

 Phrynosoma 

 Eublepharis 

 Heloderma 



Gerrhonoius 



Xantusia 



Verticaria 



Cnemidophorus 



Eumeces 



Anniclla 



Glaucoma 



Lichanura 



Charina 



Arizona 



Pityophis 



Salvadora 



Phyllorhynclms 



Contia 



Ficimia 



Chilomeniscus 



Rhinochilus 



Hypsiglena 



Trimorphodon 



Sibon 



Sistrurus 



Crotolus 



In searching for the localities which may l)e conceived to have 

 been those of the Nearctic origin of genera, it is to be observed that 

 little is to be learned from Chelonia, for the aquatic habits of most of 

 the order renders them relatively untrustworthy as guides in terrestrial 

 distribution and, furthermore, we are as yet ignorant of the characters 

 in most genera which should be regarded as primitive. Nevertheless, 

 it is obvious that conditions best favoring the development of fresh- 

 water turtles must have always been far more completely presented 

 in the well watered Atlantic subregion than in the arid Sonoran. 



In Cinosternidae the extensive range of the Atlantic species, Cino- 

 sternum pennsylvanicum and Aromochelys odoratus, favors the view 

 that they have been longest established, and it would appear further 

 that the Louisianan and Sonoran species do not exhibit any great 

 amount of differentiation from these forms. 



Of the thirteen species of Chrysemys found in the whole Nearctic, 

 ten are restricted to the Atlantic subregion. Eight of these are Austro- 

 riparian, three of them entering the Eastern. The near relationship 

 between C. concinna, C. mobilensis, C. scabra and C. rubriventris . all 

 especially numerous on the southeastern coast, points to their long 

 presence there. 



In the Nearctic, Emys and Clemmys are confined to the Eastern, 

 with the exception of one species of Clemmys on the Pacific coast, 

 but each has a representative in the Palsearctic, and Emys is known 

 from the Eocene of both continents. No reason can be assigned for 

 their present limited Nearctic range, which must be looked upon as 

 one of the anomalies of survival of ancient forms. 



The box tortoises of the genus Terrapene range everj^where east of 



