18 U. S. P. R. R. EXP. AND SURVEYS ROUTE IN CALIFORNIA. 



DIMENSIONS. Length of head, 5 lines ; greatest breadth, 4 lines ; length of body 8f inches ; 

 of tail, | inch ; total length, 9| inches. (Larger specimens have since been discovered.) 



HABITAT. Borders of the Mohave river, and in the desert of the Mohave. Always in the dry 

 sandy soil, with no vegetation whatever. Maximum size, one foot and a half; occurs in large 

 numbers, and is also seen in the desert of the Colorado, but is much less abundant, Dr. 

 Heermann not having observed it there. The river Mohave spreads itself out in the desert, and 

 there loses itself; and upon the floating sandhills near it these animals are found. The 

 Crotalus Lecontii is never seen with them. The Mohave empties into a salt lake about 15 

 miles in extent. 



GEN. OBS. I supposed that this animal might be the young of Crotalus Lecontei, but Dr. 

 Heermann informs me that the Lecontei is never found with it, and that it never attains to 

 more than a foot and a half in length, and always presents the horn-like processes above 

 described. It appears to be the representative of the Vipera cerastes, of Africa, and is found, 

 like that serpent, in desert and sandy regions, and is also slow and sluggish in its movements. 

 The genus Cerastes, proposed by Wagler and adopted by Dumeril and Bibron, it would appear, 

 should be dropped, and Vipera substituted. 



CKOTALUS LECONTEI. 



CHAR. Sulphur-yellow beneath, inclining to olive, dark spotted above, with thirty-four sub- 

 hexagonal blotches, margined with orange, the lower portion having more the form of bands ; 

 total length, 3 feet 1^ inches. 



DESCRIPTION. The head is large, depressed, the rostral plate hexagonal, high ; immediately 

 behind it, on either side, above the anterior nasal, which is very large and subquadrate, are 

 two small quadrangular plates ; posterior to these are four large plates in a single row ; a large 

 tectiform plate in front of the supraocular situated obliquely ; at its inner and posterior 

 extremity a smaller quadrangular one on each side, (the first of the supraorbitar row in some 

 specimens larger than in others ;) scales constituting the supraorbitar row rather small ; scales 

 upon the head subequal, triangular, much striated, those upon the sides much larger ; two 

 plates above the pit between the eye and nostril, and one larger one, the antocular ; two rows 

 of scales between the seventh supralabial and the scales which margin the eye inferiorly ; 

 fourteen supralabials the first large, the three next small, the rest larger than the latter ; 

 fifteen infralabials, the three first much extended inferiorly, the one most so about 2| lines in 

 extent ; body robust ; scales narrow posteriorly, not very deeply striated, strongly carinated, 

 twenty-six rows ; ground color, olive or yellow above, with thirty-four to thirty-six subhex- 

 agonal brownish blotches margined with orange, the last seven or eight having more the form 

 of bands ; four or five black bands upon the tail ; beneath, sulphur-yellow, darkly maculated ; 

 maculations most conspicuous posteriorly, neck and anterior part of abdomen comparatively 

 free from them ; chin and throat white, on either side a row of obscure spots occupying the 

 middle of the interspace between the lateral extremities of the dorsal blotches ; besides these, 

 are other spots of a similar color extending over three or four of the inferior rows of scales, and 

 confluent with the maculations upon the abdomen. 



Abdom. scuta, IfO-lTS ; sub caud., 24-22 ; all single. 



DIMENSIONS. Length of head, 1^ inch ; greatest breadth, If inch ; length of body, 2 feet ; 



