POISONOUS SNAKES OF NORTH AMERICA. 417 



Figures. — Baird, Mex. Boiiml. Surv., ii, Kept., pi. v, tig. 1 (1859). — Baird, Pac. 

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

 pi HI, lig. 6 (1874). 



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

 lateral rows smooth. Vertical plate [frontal] snbpentagonal, taperiiij; 

 posteriorly. Lateral rows of blotches proportionally very small. 



The ground color is yellowish brown, with three lateral series of deej) 

 chestnut brown blotches. Two elongated brown blotches extend from 

 the sn[)erci!i;iries [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 i»it. The lower jaw and chin 

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

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

 yellow fillet, from the head to the tij) 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- 

 uated anteriorly only. 



The blotches of the two lateral series are ])roportionally 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, bur do not extend beyond the anus, occupying the second, third, 

 and fourth rows of scales. The first and lower series attect the fii-st 

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

 dotted and sprinkled irregularly with brown. 



Scales elliptical, subtrun(;ated posteriorly, constituting 23 rows, 

 strongly caiinated, except the two lateral rows, which are suiooth 



Head, when seen from above, subelliptical; vertical plate [frontal] 

 proi)ortionally more elongated than in C. terf/eminus \ = iS. catenafns]. 



Nundjerof . eutrals[gastrosteges], 143 to 153; of caudals [urosteges], 

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



Variotion. — Tlie 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 ui)i)cr loreal separating the 

 l)reocular from the posterior nasal. 



In coloration there is considerable ditt'erence between the specimens, 

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

 thusobscuring the characteristic dark spot on the middle of the parietal 

 suture. 



Geofiruphiritl distribution. — The present subspecies rei)resents the 

 typical Massasauga in the Southwest. Curiously enough it does not 



* Original (Ipscription by C. Girard iu Baird and Girard's N.Am. iSerp., p. 15, 

 from spccmiens Nos. 506-508, U. S. Nat. Mus, 

 11, Mis, 1S4, pt. 2 27 



