NORTH AMERICAN 13ATRACHIA AND REPTILIA. 53 



h. Eyes superior, rather close together; alveolar plate 

 narrow; a small pointed projection at symphysis 

 of jaws; no scales between the costal and marginal 

 rows Chelydra. 



Genus Chelydra, Schw. 



103. C.serpentina^\!\x\w. Common Snapping Turtle, Head 

 rough, covered with soft skin; tail with two rows of large scales 

 beneatli; ridges of carapace disappearing with age; jaws moder- 

 ately hooked. Throughout the United States, except Pacific 

 sub-region. 



Genus Macrochelys, Gray. 



104. M. lacertina^ Schw. Alligator Snapper. Head very 

 large, covered with smooth, symmetrical plates; tail with many 

 small, imbricate scales beneath; carapace strongly tri-carinate; 

 the keels not disajipearing with age; jaws strongly hooked. 

 South of Missouri river, in tributaries to the Mississippi and 

 Gulf of Mexico; north to Wisconsin.* Rare. 



Family CINOSTERNID^. 



Head pointed in front; eyes situated far forward; lower jaw 

 tei-minating in a sharp point; limbs slender; feet short. 



a. Plastron small, narrow behind, with eleven scales; 

 front and hind portions very little, if at all, mov- 

 able on middle Aromochelys. 



h. Plastron larger; front and hind portions broad and 

 rounded, freely movable on middle part (except 

 often in old specimens); scales 8 to 11. Alveolar 

 plate fiat and rather broad Cinosternwrn. 



Genus Aeomochelys, Gra3^ 



105. A. odoratus^ Latr. Musk Turtle, l^o point at sym- 

 physis of upper jaw; the end of lower curved somewhat upward 

 and outward; scales of carapace not imbricated in adult; shell 

 dusky, clouded, sometimes spotted; two yellow stripes, one 

 above, the other below the eye, extending along the neck. Aus- 

 troriparian and Eastern sub-regions. 



106. A. oarinatus, Gray. Little Musk Turtle. A point or 

 chisel edge at symphysis of upper jaw; scales of keel somewhat 



*Fide Dr. P. R. Hoy. 



