Observations on the Chelonians 



of North America. III. 

 DR. R. W. 5HUFELDT, C. M. Z. 5. 



~* S" 



Aromochelys odoratus 



Common Musk Turtle 



No group of turtles in our chelonian 

 fauna are more thoroughly aquatic in 

 their habits than are those composing the 

 family Cinosternidae. Most of the spe- 

 cies are North American in the matter of 

 habitat, and herpelotologists generally 

 have relegated the eight or nine known 

 species to the two genera Aromochelys 

 and Cinostemum. They are all small 

 types, and upon comparison have pretty 

 much the same general appearance. Their 

 best differentiating characters are to be 

 seen in the plastron or ventral part of the 



shell. The inner median margins of the 

 carapace are joined by a transverse rigid 

 bridge, to which is hinged in front and 

 behind the plastronic lobes, which are 

 ligamentously hinged, and so movable. 

 They close up tightly before and behind 

 at the will of the animal, and much in 

 the same way as it is accomplished in our 

 well-known terrestrial box tortoises. In- 

 deed, so perfect is this closing in Cino- 

 stemum, that in some localities these 

 forms are known as box turtles. 



Superficially, the carapace is extremely 



