544 PROCEEDINGS OF THE ACADEMY OF [Aug., 



of a median keel, which does not appear in others, possibly female, of 

 less dimensions. The small San Antonio example shows it slightly on 

 the posterior declivity. The head is noticeably narrow and fiat; jaws 

 weak and beak feebly hooked. The feet are fully webbed and the fore- 

 claws large and strong. There is a patch of keeled tubercles above 

 the heel. 



The large El Paso specimen, which is male, is uniform greenish-olive 

 on the carapace, each shield having a narrow black border on its hinder 

 margin, most marked on the costals. The plastron, which is concave 

 and deeply striated, is yellow deepening to dark brown on the gulars 

 and anals and on the bridge. The head and neck are entirely without 

 markings, uniform dark gray above, whitish on the sides and beneath. 

 Jaws yellowish with dark brown cutting edges. Outer surface of 

 limbs dark gray without markings, lighter beneath. The largest 

 Pecos specimen is 120 mm. long and is similar, except that the back is 

 darker, the plastron decidedly green and less grooved. This is prol")- 

 ably a female. The others are colored like the last, except one from 

 Pecos 110 mm. long, which has the carapace brownish-yellow, with 

 hardly a trace of green, and the dark margins to the shields hardly 

 visible. The edge and under side of the marginals is dull orange. 

 Plastron yellow, darker in front and behind. 



Compared with PL XVII in the Wheeler Survey, to which the name 

 C. flavescens is attached, all my specimens have the shell narrower and 

 more regularly oval; the head and neck are noticeably flat and narrow, 

 and the pectoral shields are nearly triangular and form an exceedingly 

 short suture as in pennsylvajiicum, instead of the wide one shown by 

 the plate. 



This species is nearly related to pennsylvanicuni, but as far as 

 present material goes, is amply distinguished by its form of head and 

 by color characters. 



Its geographical limits remain to be established. All the specimens 

 I have seen are Texan. 



Chrysemys mobilensis (Holbr). 

 Chrysemys elegans (Wied.). 

 Terrapene ornata (Agass.). 



LAOERTILIA. 



Crotaphytus collaris (Say). 



Some of the Pecos specimens exhibit the double row of inter- 

 orbitals attributed to C. haileyi Stej.^ I have also a number of 



' No. Am. Fauna, No. 3, p. 103, PL XII, fig. 1. 



