2420 



TORTOISES, TURTLES, AND PLESIOSAURS 



Three remarkable tortoises inhabiting tropical Africa constitute a 

 10 T" ' g enus distinguished at a glance from the other members of this sec- 

 tion of the family by the circumstance that the hinder portion of the 

 carapace is articulated to the anterior moiety by a ligamentous hinge, upon which 

 it is freely movable, so that when the animal is withdrawn the hinder extremity of 

 the shell can be completely closed. This hinge runs between the fourth and fifth 

 costal bones and the seventh and eighth marginals of the shell. The skull agrees 

 with that of the preceding genus, in the absence of a median ridge on the front of 

 the palate, while the neural bones of the carapace are hexagonal and short sided 

 behind, and the caudal shield is undivided. The costal bones of the carapace differ, 

 however, from those of the tortoises before described, in being of nearly equal 

 width throughout, instead of alternately narrow at one end and broad at the other. 

 Of the three species of the genus, the dentated hinged tortoise (Cimxys erosa) from 

 Guinea and the Gabun is characterized by the front and hind margins of the cara- 

 pace being everted and strongly dentated; by the absence of a nuchal shield, the 

 projection of the extremity of the plastron in front of the carapace, and the sloping 

 contour of the hinder extremity of the latter. The length of the shell is nine 

 inches; its general color above being dark brown, with lighter centres to the shields, 

 and the lower sides of the costal shields yellowish; while on the plastron the 

 shields have dark brown centres and yellowish margins. In the nearly allied 

 Home's hinged tortoise (C. homeana] from the same regions there is a nuchal 

 shield, the extremity of the plastron does not project in advance of the carapace, and 

 the hinder extremity of the latter descends vertically. On the other hand, in Bell's 



hinged tortoise (C. belliana), 

 which ranges right across tropi- 

 cal Africa, the margins of the 

 carapace are neither everted nor 

 serrated; a nuchal shield being 

 present on the front of the cara- 

 pace. In length the latter does 

 not exceed seven and one-half 

 inches. 



In habits the hinged tor- 

 toises show a complete transi- 

 tion from the land tortoises to 

 the terrapins, and thus fully 

 justifies the conclusion, arrived 

 at from structural considera- 

 tions, that both groups should 

 be included in a single family. 

 According to the observations 



of Monteiro, it appears that Bell's hinged tortoise is essentially a land reptile, in- 

 habiting regions formed of gneiss rocks or other dry localities, where it is active 

 during the hot rainy season, but in the cooler portion of the year, from May to 

 October, according to native reports, lies deeply buried in the earth. Both the 



BELL'S HINGED TORTOISE. 



