POISONOUS SNAKES OF NORTH AMERICA. 425 



Description* — Muzzle broad; rostral small. Scales between super- 

 ciliaries [supraoculars] small, uniform, except the two anterior. Two 

 frontal plates [iuternasalsj, 4 postfrontal [prefrontals], 2 intersupercil- 

 iary [interorbitals],aIl in contact. Five rows scales between the labials 

 and suborbital row; middle row not extending beyond the middle of 

 the orbit; labials, 18 above, fifth and sixth largest; 17 below. Dorsal 

 rows of scales, 20; two external rows, small. Tail uniform black. Color 

 roll sulphur; a series of chestnut-brown transverse lozenges [fig. 53] 

 with exterior corners produced to the abdomen ; centers of lozenges 

 with one or two spots; each scale but one color; a brown patch below 

 and behind the eye. 



One of the most strongly marked of all species. Head very broad in 

 front; outline nearly rectangular. Rostral small. Two anterior front- 

 als [interuasals]; behind these, four plates, the exterior resting on the 

 superciliary; behind these two other plates, between and in contact 

 with the superciliaries [supraorbitals]. Anterior nasal subtriangular. 

 Top of head with numerous smooth subtuberculous scales. Suborbitals 

 large, extending to the anterior canthus. General aspect smoother than 

 in crotali generally; scales rounded at the posterior apex, carinatedbut 

 slightly. 



General color above, that of roll sulphur; beneath, pale yellowish; 

 posteriorly, very faintly clouded with brownish. Tail black. Anteri- 

 orly the scutelUe [ventrals, or gastrosteges] are entirely immaculate. 

 Along the back is a series of transverse reddish or chestnut-brown 

 lozenges embraced in a width of 12 or 11 scales and 4 or 5 scales long, 

 and with the exterior angles produced to the abdomen [fig. 53J. 

 These lozenges are frames with the outline generally one scale in 

 width and with the centers of the ground color; sometimes divided by 

 a median line of brown so as to show two yellowish sjwts inside of the 

 lozenges. The scales exterior to the lozenges are rather lighter. 

 Sometimes the brown rings and the lozenges widen at the abdomen 

 and indicate lateral spots of four scales; at others, and especially ante- 

 riorly, the rings are obsolete and the brown is in a dorsal series. In 

 fact for the anterior fourth of the body we have a dorsal patch of brown 

 showing alternately, at successive intervals, one large yellowish spot 

 and then a pair of smaller ones, owing to the confluence of the suc- 

 cessive lozenges. The superciliaries and scales anterior to them, as 

 well as broad patch below and behind the eye, light greenish-brown. 

 Tail uniform dark-brown above, paler beneath. 



A remarkable character of this species is that each individual scale 

 is of the same uniform tint to its base, and not showing two colors as 

 in other species. 



Variation. — The head scutellation of the present species is exceed- 

 ingly variable. I have seen about nine specimens, hardly two of which 



* Original description by S. F. Baird, in Baird and Girard's N. Am. Serp., p. 10, 

 from a specimen from New Mexico,- U. S. Nat. Mus., No. 485. 



