POISONOUS SNAKES OF NORTH AMERICA. 417 



Figures. — Baird, Mex. Bound. Snrv., ii, Kept., pi. v, fig. 1 (1859). — Baird, Pac. 

 R. R. Rep., X, Rept., pi. xxv, fig. 10 (1859).— Jan, Icon. Ophid. livr. 46, 

 pi III, fig. 6 (1874). 



Description* — Twenty-three rows of dorsal scales; first and second 

 lateral rows smooth. Vertical plate [frontal] siibpeutagonal, taperiiig- 

 posteriorly. Lateral rows of blotches proportionally very small. 



The gronnd-color is yellowish brown, with three lateral series of deep 

 chestnnt brown blotches. Two elongated brown blotches extend from 

 the superciliaries [supraoculars] backward. A narrow band of chestnut 

 brown, from the posterior frontal plates [prefrontals], passes over the 

 eyes to the neck, under which a yellowish stripe extends from the nos- 

 tril to the angle of the mouth. The snout and upper Jaw are brown, 

 with two yellow" fillets diverging from the pit. The lower jaw and chin 

 are mottled with brown and yellow. There are about 42 dorsal brown 

 and irregnlar blotches, margined with deep black and encircled with a 

 yellow fillet, from the head to theti]) of the tail, the thirty-fourth oppo- 

 site the anus, the last three passing to the sides of the tail, but do not 

 meet below. Subcircular on the posterior half of the body, the blotches 

 on the anterior half are longer transversely than longitudinally, emargi- 

 nated anteriorly only. 



The blotches of the two lateral series are proportionally small. 

 The blotches of the upper series are more or less obsolete, and alter- 

 nate with the dorsal ones. Those of the second lateral series are the 

 smallest, and alternate also, being of as deep a color as the dorsal 

 ones, but do not extend beyond the anus, occupying the second, third, 

 and fourth rows of scales. The first and lower series affect the first 

 and second rows and only one scale. The belly is of a light straw color, 

 dotted and sprinkled irregularly with brown. 



Scales elliptical, subtruncated posteriorly, constituting 23 rows, 

 strongly carinated, except the two lateral rows, which are smooth. 



Head, when seen from above, subelliptical; vertical i)late [frontal] 

 proportionally more elongated than in C. tergeminus [ = tS. catenatus]. 



Number of ventrals[gastrosteges], 143 to 153; of caudals [urosteges], 

 24 to 31 ; scale rows across middle of body, 23. 



Variation. — The chief variation in scutellation I have found in this 

 subspecies consists in the occasional separation of the anterior prolon- 

 gation of the preocular so as to form an upper loreal separating the 

 preocular from the posterior nasal. 



In coloration there is considerable difference between the specimens, 

 chiefly consisting in an obliteration of the markings on top of the head, 

 thus obscuring the characteristic dark spot on the middle cf the parietal 

 suture. 



Geographical distribution. — The present subspecies represents the 

 typical Massasauga in the Southwest. Curiously enough it does not 



* Original description by C. Girard in Baird and Girard's N.Am. Serp., p. 15; 

 from specimens Xos. 506-508, U. S. Nat. Mus. 

 H. Mis, 184, pt. 2 27 



