92 [June, 



Dimensions. Length of head 1 inch ; breadth f ; length of carapax 6 inches, 

 measured along curvature superiorly ; breadth at middle 5| inches ; of tail 2. 



Habitat. Posa Creek, Lower California, where it occurs in great numbers. 



Gen. obs. This species resembles none ol the North American Emydes with 

 which 1 am acquainted. Its dark color puts one in mind of, but is not so jet a 

 black as that of Sternothaerus niger of Madagascar. 



SAURIANS. 



Dipso-saurtjs, Hallowell. 



Gen. char. Head triangular, covered above and in front with tubercles ; nos- 

 trils latero-superior, opening in a single scale ; rostral plate veitical, triangular; 

 jaws margined each with a series of smooth quadrilateral plates ; tympanum 

 visible, depressed ; upper part of body covered with carinated scales, more or 

 less rounded posteriorly, arranged in oblique rows ; a row of scales much larger 

 than the rest along the dorsal line, and much more strongly carinated, forming 

 a slight dorsal crest; a gular fold ; scales of abdomen quadrangular, smooth ; 

 femoral pores ; tail covered with transverse rows of verticillate and carinated 

 scales* 



DlPSO-SAURUS DORSALIS. 



Sy?i. Crotaphytus dorsalis, Baird and Girard. Proceed. Acad. Nat. Sc. 1852, 

 p. 126. 



Coloration. Body presenting numerous lines of red upon the sides, with 

 blotches of the same color over the shoulders, the intervening spaces numerous 

 white spots; upper surface and sides of tail marked with red spots arranged in 

 transverse rows ; upper surface of extremities with red ; throat, abdomen, under 

 surface of extremities and tail white. The coloration, as described by Profs. 

 Baird and Girard, appears to be taken from younger specimens, one such before 

 me corresponding with it precisely. 



Dimensions. Length of head 7 lines; breadth 7 ; length of head, neck and 

 body to vent, 8 inches, (Fr.) ; of tail lh inch.; anterior extremities 1 inch. ; 

 posterior 3 inches to extremity of nail of longest toe. 



Habitat Desert of the Colorado, to which it appears to be confined. The 

 smaller specimen from near Fort Yuma, the large one found in the desert be- 

 tween Rum River and the Tejon Pass, (pronounced Tahon ;) a country without 

 water, not sandy, but arid, bearing artemisia, &c. 



Gen. remarks. This animal differs from Crotaphytus (Holbrook) in having 

 the upper part of the body covered with quadrangular scales, instead of granula- 

 tions, and the larger row of carinated dorsal scales giving rise to a slight crest, 

 no trace of which exists in Crotaphytus, from Leiolepis in having tubercles, and 

 not plates, upon the head and from Homalo-saurus in the form of the marginal 

 plates of the upper jaw. 



Uro-saurus, Hallowell, 



Gen. char. Body very slender, which, as well as the head, is much depressed; 

 scales upon the back much larger than those upon the sides, and strongly cari- 

 nated ; nostrils superior in a single scale; head covered with plates ; aural aper- 

 tures very distinct ; a gular fold ; extremities slender; toes 55 ; tail very long 

 and tapering, verticillate ; femoral pores, but no anal ones. 



Uro-saurus graciosus, nob. 



Sp. char. Head yellow, with a few brow r nish marks; seven longitudinal rows 

 of scales upon the back very distinctly carinated. Color of body yellowish, 

 mixed with brownish and black spots ; extremities yellowish, with dark colored 

 transverse bands ; tail of same color above as body ; under surface silvery white, 

 with blackish spots; eleven femoral pores. 



Dimensions. Length of head 5-8ths inch; greatest breadth f inch; length 

 of head, neck and body to vent, If inch j of anterior extremities to extremity of 



