TORTOISES AND TERRAPINS. 



47 



series of infi-amargiuals. They differ by the open temporal region 

 of the skull, as well as by the small size or absence of the gular 

 shields, and the short tail. Some of the hinder costal plates overlap 

 the nearals so as to meet in the middle line. In Dermati'mys (74) the 

 large plastron, which is firmly joined to the carapace, carries at least 

 eleven shields, and there are four inframarginals. In Stauroty- 

 pus (73) the plastron is cruciform, with the front flap movable, and 



Fig. 50. 



fflQDirha 



Temminck's Snapper, or Alligator-Terrapin {MacrocU'inmys temmincki) ', 

 J nat. size. (No. 75-) 



seven or more shields ; the number of inframarginals being two. 

 Nothing is known of the habits of either group. 



The Mud-Terrapins (family Cinostermdcc, 66-72) resemble the 

 Ghehjdridce, and Deimatemydidce, in the presence of rib-like processes 

 to the nuchal bone of the carapace, but differ from these and all other 

 Chelonia in the absence of an entoplastral bone to the plastron, which 

 thus has eight, in place of the usual nine, bones. The neck can 

 be completely retracted within the shell, the temporal region of the 



