2 28 VERTEBRATE ANIMALS OF THE UNITED STATES 



plastron well developed, with movable anterior and posterior lobes, 

 covered with 9 to ii plates and joined with the carapace by narrow 

 bridges; toes 5-5; claws 5-4; feet webbed; head pointed; jaws strong: 

 14 species, all American, 7 in the United States, inhabiting slow streams 



Fig. 129. — Tail of Chelydra serpentina {from Surface). 



and muddy ponds, and eating animal food; eggs elliptical; all the 

 species emit a musky odor. 



Key to the Genera of the Kinosternidae 



ai Plastron narrow, not capable of closing the shell i. Sternotherus. 



a2 Plastron broad, capable of closing the shell 2. Kinosternon. 



1. Sternotherus Gray. Musk turtles. Plastron reduced, scarcely 

 movable: 3 species. 



S. odoratus (Latreille). Musk turtle. Carapace 90 mm. long 

 and 60 mm. wide; color brownish, often striped or blotched with a 

 darker color; plastron yellowish or brown; head large, with strong 

 jaws; plastron 68 mm. long and 31 mm. wide; side of head with 2 narrow 

 yellow stripes, one passing above and the other beneath the eye : eastern 

 and central States, from Canada to the Gulf; westward into Missouri 

 and Texas; common; odor of musk strong. 



S. carinatus (Gray). Similar to S. odoratus but with a prominent 

 middorsal keel and with imbricated plates; head spotted with black, 

 without stripes: Mississippi, Louisiana and Texas. 



2. Kinosternon Spix. Mud turtles. Plastron with central plate 

 and 2 movable lobes, capable of closing the shell: 10 species, 5 in the 

 United States, North and Central America, barely entering South 

 America. 



Key to the United States Species 



ai Bridge very short, about a third the length of fore lobe of 



plastron K. steindachneri. 



ao Bridge longer, about half the length of fore lobe of plastron. 



bi Fore lobe shorter than hind; carapace with 3 yellow stripes. .A^. haurii. 

 ht Fore lobe as long or longer than hind. 



Ci Head spotted with yellow A', subruhrum. 



C2 Sides of head bright yellow K. JIavescens. 



C3 No yellow on head or body K. sonoriense. 



