438 REPORT OF NATIONAL MUSEUM, 1893. 



C. adamanteus ; a narrow light line from the posterior end of supercil- 

 iary backward directly to the angle of the mouth; a second from the 

 anterior extremity, nearly parallel with the first, the two inclosing an 

 indistinct patch and separated on the labials by 4i scales. There is 

 also a single narrow light line across the superciliary perpendicular 

 to its length, obsolete in old specimens. 



It may readily be distinguished from C. <((!(( manteus by its light color 

 and the truncations of the rhomboids, as well as the general obsolete- 

 ness of the lateral markings. The rhomboids are longer in proportion 

 and more roiTuded. The 2 lateral rows of scales are smooth, the next 

 2 more strongly carinated than in C. adamanteus. The fifth upper 

 labial is largest, and transverse, the rest nearly uniform. The stripes 

 on the side of the head are less distinct. 



From C. confiuentus it may be distinguished by the greater compara- 

 tive size of the interval between the dorsal blotches, especially poste- 

 riorly. In G. conlinenius there are two light lines across the supercil- 

 iary plate, dividing it into three sections, the central rather narrower. 



Here, too, the j)osterior facial stripe, instead of passing to the angle of 

 the month, goes back of it on the second row above the labials, in C. 

 atrox, passing directly to the angle of the mouth. Other important 

 distincti(ms are seen in the narrower scales of C. confluentus, etc. 



From C. lueife)\ the more narrow head, fewer and larger intersuper- 

 ciliary scales, lighter color, arrangement of color along the head, will 

 at once distinguish it. 



Number of ventrals (gastrosteges), 177 to 187; number of subcaudals 

 (urosteges), 23 to 28; number of scale rows across the body, 25 to 27. 



Variation. — This species exhibits a considerable variation in the 

 scutellation, less so in coloration. The ground color is usually more or 

 less grayish, with a varying amount of brownish, olive, or yellowish 

 admixture, while on the Pacific coast there seems to be a reddish form, 

 geographically liinited, which will be considered separately as a race. 

 The head pattern is fairly constant and will at once serve to distinguish 

 this species from C. adamanteus, the nasals and anterior labials being 

 unicolor, densely dusted over with minute black dots. 



As for the scutellation, the greatest variation is shown in the pres- 

 ence, or absence, of an upper loreal, as well as in the size of the scales 

 or scutes covering the upper surface of the snout. In a number of 

 specimens the upper head scales are more or less enlarged, in some 

 forming on the snout a series of paired scutes reaching to between the 

 orbits, very much after fashion of C. molossus and its nearest allies. 

 This character, however, is shared by specimens belonging to other 

 species, for instance C. horrid ns, and notably in C. coniiuentus, so much 

 so, in fact, that the so-called C. scntulatus, which is based upon such 

 specimens, is composed of specimens of both species. The character 

 is mostly exhibited4n specimens from the Mexican tableland and its 

 extension into Arizona, but it is apparently not constant enough to 



