368 Dll. H. GADOW OX EVOLUTION [Mar. 20, 



Key to the S'pecies cbc. of the TESSELLATUS-Groiij). 



Nasal not touching second labial. 

 Throat pale, not spotted. 



7 stripes, no field-spots. Length 86 mm. 



New Mexico. C. ;perplcxus. 



8 stripes, no field-spots. Length 60 mm. 



Nuevo Leon. C. octoUneatus. 

 No stripes, no field-spots. Length 56 mm. 



Nuevo Leon. C. inornatus. 

 Throat pale, with dark spots. 



Brown marbled. Length 120 mm. 



Lower California. C. maximus. 

 With field-spots and stripes, ultimatelj' spotted 



and barred with black and white. Length . ^ usselJatus. 



102 mm South-western U.S. A. ] _ steineaeri 



Becomes unicoloured, with 3 rows of blackish ^ J m • 



spots. Thighs and tail below vermilion. 

 Length 100 mm. San Margarita Island, 



West Lower California. C rubidus. 

 Throat and rest of under parts blackish. 



Vermiculated and spottM on bluish ground. . ^ ^^ 



Length 86 mm , Nortli Mexico to Arizona. | _ ^ variolosus. 

 Monochrome blackish. Length 82 mm. ^ 



Sonora and San Martyr Island, Gulf . ^ ,„«,.^ .;,. 



of Cahtornia ) =C retJ'ons 



Nasal in contact with second labial. ^ ' " -P • 



Only 12 or 13 pores. Length 55 mm. 



Cedros Island, Lower California. C. labialis. 



Tessella TVS- Group . 



Definition. — Cnemidopho^^us with 4 supraoculars, a collar com- 

 posed of many small scales, and the posterior side of the forearm 

 covered with granules only. 



This group, centi-ed in Sonoraland, is composed of a great 

 number of definable forms and has a very wide distribution ; 

 roughly speaking, from San Francisco across Nevada to the Great 

 Salt Lake, thence south-eastwards thi'ough the whole basin of 

 the Rio Grande down to Laredo, from El Paso to Hermosillo in 

 Sonora, and from the southern end of Lower California again to 

 San Francisco. Nearly the whole of this wide range is inhabited 

 by the central form C. tessellatus with its correspondingly greatest 

 amount of variation in structure and pattern of coloration. Almost 

 all the other forms are rather local. 



CxEMiDOPHORUS PERPLEXUS Baird. 



Unfortunately only two specimens of this apparently least 

 specialised kind could be examined. Some have been recorded 

 from the Yalley of the Rio Grande near and north of El Paso ; 

 others from Pecos in Texas by A. E. Brown, Proc. Acad. Phil. 

 1903, p. 547. 



According to Cope, the colour-characters are the possession and 

 retention of 7 stripes, absence of pale spots in the fields, and 

 absence of dark spots on the throat and on the rest of the under 

 parts. Larger humeral scales in 4 rows, femorals in 6 rows, 

 cotmting from the largest to the pores which number 19 ; size 

 from snout to vent 86 mm. 



