46 GUIDE TO EEPTILES AND AMPHIBIANS. 



Pig. 49. 



Skeleton of a Land Tortoise, in a vertical section through the carapace, 

 showing the mode of retracting the neck in a vertical plane. 



c, neck; v, dorsal vertebrae ; t, tail; r, costal plates of carapace; pi, plastron; 

 s, shoulder-bones ; p, pelvis. 



or Snappers, two are from North America, while the third is from 

 Ecuador ; fossil species occur in the Tertiary rocks of Europe. The 

 nuchal bone of the carapace has rib-like processes underlying the 

 costals. The large head (which is furnished with a beak) and neck 

 cannot be withdrawn into the shell ; and the temporal region of the 

 skull is partially roofed. The long tail has the articular surfaces of 

 most of the vertebrae cupped behind. Inframarginal horny shields 

 separate the marginals of the carapace from the abdominals of the 

 plastron, which is cruciform and united to the carapace by a narrow 

 bridge. Temminck's Snapper {Macroclemmys femmincU, 75, fig. 50) 

 has a ridged, while the two species of Chelydra (76 and 77) have a 

 smooth shell. 



Snapping Turtles live in deep pools or sluggish streams, keeping 

 mostly to the bottom, although rising from time to time to breathe, 

 and occasionally landing. They are carnivorous, feeding on fish 

 and waterfowl, and inflict dangerous bites. 



The Tortoises of the small Central American family Dermatemydiche 

 (73 and 74), for which there is no collective English name, resemble 

 the Chelydridce in that the nuchal plate of the carapace gives off a pair 

 of rib-like processes underlying the costals ; and also by the pectoral 

 shields of the plastron being separated from the marginals by a 



