Species of North American Tortoises. 93 



young ones always,) more or less jointed : marginal plates 

 twenty-three, sternal eleven. 



Third. — Such as have the sternum joined to the shell by a 

 membrane, as in the T. clausa : in this the sternum is bivalve, 

 but whether this should be taken as a generic mark, remains yet 

 to be determined. Some European species, I believe, have the 

 sternum joined to the shell in the same manner : marginal 

 plates twenty-five, sternal twelve. 



Fourth. — Such as have the sternum joined to the shell by 

 wings, which are a prolongation of the pectoral sections alone, 

 the abdominal being wanting,) and the supplementary plates 

 interposed between the shell and the wings : marginal plates 

 twenty-five, sternal ten. This is our T. serpentina. 



These observations relate only to the Tortoises which are 

 natives of our country ; how fai- they may be applicable to 

 those which inhabit Europe and Asia it is impossible to say, as 

 there is no possibihty of inspecting a numerous collection 

 of the species of this geijius. 



1. TRIONYX. 

 1. Trionyx ferox. 



Testa cartilaginea, ovalis, integerrima, antice ad marginem 

 tuberculata, disco lineis brevibus, longitudinalibus, tuberculatis : 

 OS labiatum, antice nudum, labiis revolutis oppositis : pedes an- 

 tici squamis tribus latis et acutis supra et antice, et duobus 

 tuberculis oblongis postice instructi; pedes postici squama 

 unica infra et postice : cauda brevis. 



Testudo ferox, Gmel. «Sz;c. T. cartilaginea, ejusd. T. Bod- 

 daerti, Sclineider. Leipz. Mag. zur. Natur. und CEcon. 1706. 



