i8 REPTILES AND BATRACHIANS 



Terrapins, the anterior and posterior lobes of the plastron 

 are movable and connected with the central part by 

 hinges, so that their oval-shaped shell can be partly or 

 completely closed. The mobility of the plastron varies 

 considerably according to species and with age, for, as in the 

 case of all Terrapins with hinged plastrons, the mobility 

 is not so marked in the young. The species most fre- 

 quently seen in captivity are the Pennsylvanian Mud 

 Terrapin, C. pennsylvanicum ; the Stink-pot Mud 

 Terrapin, C. odoratum ; and the Blood-stained Mud 

 Terrapin, C. cruentatum. The two former are distributed 

 throughout the Eastern States of North America, while the 

 latter is confined to Central America. 



In C . pennsylvanicum and C. cruentatum the plastral lobes 

 are freely movable ; the plastron, however, in the former 

 species, is small, and consequently does not close up com- 

 pletely against the rim of the carapace, as in the case of 

 the latter. The end of the tail is provided with a horny, 

 nail-like appendage in both sexes in C. pennsylvanicum^ it 

 is present only in the female in C. cruentatum^ and is absent 

 in both sexes in C odoratum. In the latter species the 

 plastron is considerably narrower and smaller than in the 

 two preceding, and the lobes are only feebly movable. 

 This terrapin derives its name from the fact that on being 

 alarmed it emits from certain glands a remarkably pungent 

 and most disagreeable odour of musk. 



The members of this family, none of which exceed a 

 shell length of six inches, are found in muddy ponds or 

 ditches, feeding on small fish and tadpoles. They are 

 very treacherous creatures ; when handled they immedi- 

 ately withdraw into their shells, firmly closing them ; they 



