LADY TUETLE. 665 



their habits are remarikably similar. 0. marginata ranges as far 

 north as Lake Superior, and, in the latitude of Ann Arbor, Michigan, 

 has been found out of winter quarters as late as October 22, and in the 

 spring on March 31. Theyundoubtedly attain to a good age. Aplastron 

 before me of this species was discovered in Sharon, Wastenaw county, 

 Michigan, in 1838, by Dr. C. B. Porter, who inscribed the date and his 

 name upon it. The animal was again discovered within half a mile of 

 same spot in 1868 The size of the letters and figures show that the plastron 

 could not have grown perceptibly during this period of thirty years. 

 From this and other cases where people have inscribed their names and 

 dates upon them, we may safely conclude that some, if not all, of our 

 land and fresh water turtles wander to but a short distance, grow slowly, 

 if at all, after attaining a length, in this species, of eight inches. In the 

 case of Cistudo clausa, sixty years elapsed between the time of the in- 

 scription and its rediscovery, and it then, as in this species, was found 

 within half a mile of the place where it was originally marked. 



FAMILY CINOSTERNIDiE. THE CINOSTERNOID 



TURTLES. 



Feet palmate ; toes four or five, fingers five ; oarapax high, narrow and composed of 

 hard osseous plates ; plastron small, between ornoiform and elliptical, with only seven, 

 nine or eleven shields; marginal plates twenty- three, vertebrals five, narrow, becoming 

 broader posteriorly ; eostale large, four on each side ; margins of carapax taming down- 

 ward and inward instead of outward ; head pointed ; sockets of eyes deep, 

 t Plastron oval with movable hinge between the pectoral and preanal plates, allowing 



it to clos« the shell Cinosternum. 



X Plastron crnciform ; no movable hinge behind ; incapable of closing the shell. 



Aromochelys. 



Gbnus CINOSrERNUM. Spix. 



Head snb-qnadrangnlar, pyramidal and broad; superior maxillaries rather widely 

 separated behind ; jaws slightly hooked with an inframental papilla; cranium with a 

 single rhomboidal plate; plastron oval; pectoral and preanal plates articulated by a 

 movable suture allowing the animal to close the shell; vertebral plates somewhat im- 

 bricate ; tail long, and nngniculate in the males. 



Cinosternum pennsylvanicum Bosc. 



Mud Tortoise. 



Tettudo penntylvanica, Gmelin, Schosppf, Latrbilijc, Shaw, Daudin, Edwards. 



Emy8 pennsylvaniea, Schweiggbr, IIahlan. 



Terrapene pennsylvaniea, Mkrrbm, ScuI^z. 



CUiudo pennsylvaniea, Say, ; 



