HINGED TORTOISES. 63 



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 described above, 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 (Cinixys 

 erosa), from Guinea and the Gabun, is characterised by the front and hind margins 



DENTATED HINGED TORTOISES nat. size. 



of the carapace 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 9 inches ; its general colour 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 (G. homeana), from the same regions, there is a nuchal 

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

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

 hinged tortoise (C. belliana), which ranges right across tropical Africa, the margins 

 of the carapace are neither everted nor serrated ; a nuchal shield being present on 

 the front of the carapace. In length the latter does not exceed 7J inches. 



