The Musk or Mud Turtles 



The lobes of the plastron are very wide and when closed 

 against the upper shell, form such a perfect union that it is diffi- 

 cult to insert a straw between any portion. The general effect 

 of the under surface is quite different than with the species 

 considered except C. henrici, as the bridge of the plastron is very 

 flat — in fact, it cannot be termed a bridge, for the entire sur- 

 face of the under shell is flush with the edge of the carapace. 

 The characteristic notch at the rear of the plastron, is but 

 feebly represented. 



This species has a large head and strong jaws. The tail 

 of male specimens terminates in a nail-like spine. 



Coloura1ion.^J\ke. the majority of the species the upper 

 shell is dull olive or brown, the shields narrowly bordered with 

 black. The plastron is pale yellow, with clouded brown mark- 

 ings at the edges of the shields. 



The head is dull yellow, speckled or marbled with black. 



Dimensions. — The measurements given are of an adult 

 specimen (male) from Sinola, west coast of Mexico: 



Length of Carapace 6 inches. 



Width " " 3f " 



Length of Plastron 5J 



Width of Front Lobe, at Hinge 2I 



" Rear " " " 2I 



Width of Head ij " 



Distribution. — Mexico, generally in slow-running streams 

 and rivers. 



37 



