49. KINOSTERNON 971 



large, somewhat pointed, covered with smooth skin. Chin 

 and throat with a few barbules. Limbs covered with smooth 

 skin except close to toes; anterior with five, posterior with 

 four toes, completely webbed. Tail of moderate length, end- 

 ing in a horny nail or claw. 



The carapace is yellowish olive, the plastron lighter, yel- 

 lowish. The horny plates are margined with dark brown, 

 especially along their posterior edges, above. The head and 

 neck are olive above, yellowish below, sometimes with a 

 light yellowish streak along the side of the neck, but with 

 little if any marbling or mottling, the chin and throat 

 especially being usually immaculate. 



Length of carapace 85 97 107 117 120 131 



Length of plastron 77 82 99 99 97 105 



Width of carapace 65 72 86 81 84- 92 



Width of plastron 55 56 67 65 69 72 



Remarks. Series of specimens of this and the preceding 

 species show much variation in size, shape and coloration. 

 Both species have been recorded from Arizona j indeed one 

 of the types of K. flavescens was said to have come from the 

 Gila River near Fort Yuma. Nevertheless, I incline to the 

 opinion that it ultimately will be found that all Arizonan 

 specimens represent one variable species or subspecies, those 

 of Texas, another. Variation is great and identification diffi- 

 cult. Texan specimens (K. flavescens) have fewer barbules 

 on the chin and neck, especially on the lateral fold, and the 

 skin of the neck is less granular than in Arizona specimens 

 (K. sonoriense). The shell in Texas specimens often is 

 more rounded and smoother, with less evident dorsal ridge. 

 The pectoral plates usually have a shorter median suture 

 than is seen in Arizonan examples. The color of the shell in 

 K. flavescens, usually is a little more yellowish and the dark 

 margins of the plates more distinct. The neck and chin are, 



