288 VERTEBRATES I REPTILES. 



range of differences, that Agassiz suggests its subdivision 

 into about five sub-families. Most of its members inhabit 

 bogs, marshes, still streams, and ponds. Some, however, 

 live upon the land ; nearly all are perfectly harmless. 

 Their food is both vegetable and animal. Their eggs 

 are more or less elongated, and covered with a shell 

 which is in most cases flexible. About a dozen genera 

 and about twenty species belong to North America. 



The Genus Pseiidemys, Ptychcmys, Ag., contains the 

 Red-bellied Terrapin, Ps. serrata, Gray, Ft. rugosa, Ag., 

 Emys rubriventris, Lee., of the Middle States, which has 

 the shell about eleven inches long; the Mobile Turtle, 

 Pt. mobilensis, Ag., which has the shell fifteen inches 

 long ; Ps. concinna, Gr., Pt. concinna, Ag., of the South- 

 ern States, which has the shell about eight inches long, 

 dusky, and marked with yellow lines ; and Ps: hieroglyphi- 

 ca, Gr., Pt. hieroglyphica, Ag., of the Middle, Western, and 

 Southern States, which has the shell over eight inches 

 long, olive brown, reticulated with brownish orange. 



The Genus Trachemys contains three species, common 

 in the Southern and Western States, T. scabra, Ag., 

 T. Troostii, Ag., and T. elegans, Ag. 



The Genus Graptemys contains the Geographical or 

 Map Turtles, of the Middle and Western States. 



The Genus Malacoclemmys contains the Salt-water Ter- 

 rapin, M. palustris, Ag., E. terrapin, Holbr., of the salt- 

 water marshes from New York to South America, which 

 has the shell about seven and a half inches long. 



The Genus Chrysemys contains the Painted Turtle, 



C. picta, Gray, from New Brunswick to Florida, and west- 

 ward, which has the shell about six and a half inches 

 long, nearly black, with yellow lines, and the marginal 

 plates generally marked with bright red. 



The Genus Deirochelys contains the Reticulated Turtle, 



D. reticulata, Ag., of the Southern States. 



