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U. S. P. R. R. EXP. AND SURVEYS-ROUTE IN CALIFORNIA. 
and shining, their posterior margins rounded, the three inferior rows larger than the others ; 
gastrostiga appearing to a slight extent upon the flanks ; tail short, with a somewhat blunt 
extremity. 
Coloration. —Milk white above, with thirty-four transverse black bands, including one upon 
the posterior part of the head; six complete rings of black upon the tail, and one incomplete 
just behind the anus ; jaws, chin, throat and abdomen white; interspaces between rings upon 
under part of tail white.—Abdom. Scuta. 158, Sub. Caud. 34. 
Dimensions. —Length of head, 4 lines ; breadth, 2\ lines ; length of body, 9 inch 9 lines ; of 
tail, 1 inch 7 lines ; total length, 9 inches. 
Habitat. —Mohave Desert. 
Gen. Obs. —This serpent resembles no other figured in North America, and is therefore easily 
recognised. In the genus Sonora of Professors Baird and Girard, there are, according to them, 
three postoculars, and two nasal plates on each side with the nostril between them. In Sonora 
semiannulata there are twenty-five transverse black hands upon the body, and six complete 
rings upon the tail. The rings in Col. ( Zacholus ) zonatud of Blainville, completely surround 
the body. The nostrils, according to Blainville, open between two plates, hut Wagler has 
them each in a single plate, “in medio scutelli sitis,” in his definition of Zacliolus. Wagler, 
however, cites Col. Riccioli , Metaxa. Serp. Rom. as appearing to belong to this genus, “scheint 
als Gattung zu gehoren,” hut C. Bonaparte represents the nostrils as placed in the commissure 
between two scuta “ gli narici sono situate alia commissura di duo scutelli nasali.”* Blainville 
represents two half rings upon the head. Zacholus zonatus is probably allied to Coronella 
balteata. 
The animal above described approaches very much Simotes in the configuration of the plates 
upon the head ; hut in Simotes the nostrils open between two plates, and the frenal is quite 
different in shape, being much higher, and not long and slender. The head is also much more 
robust in Simotes, the body rounded and not flattened, and the tail pointed. The posterior 
teeth are also longer. The plates upon the upper part of the head are very different from those 
of Homalosoma, an African genus. The rostral is remarkable, from the fact that so much of it 
occupies the anterior portion of the upper part of the snout, where, as before remarked, it is 
triangular in shape, the apex of the triangle passing deeply backward between the internasals. 
This is also the case in Simotes, and to a greater extent in Rhinostoma ; hut in Simotes the snout 
is conical; the frontal plate resembles both that of Simotes and Rhinostoma, hut is less broad ; 
the prefrontals and rostral are very different in Rhinostoma, as is also the shape of the body, 
and the scales in the latter are longer and more hexagonal. Rhinostoma nasicum is a much 
larger animal. In the specimen in our museum, from Venezuela, which appears to belong to 
this genus, the nostrils are between two plates, the frenal is more or less quadrangular ; there 
are two antocular and three postoculars, and the rostral plate is rounded, retroussi, with a 
sharp and well defined edge. 
* In Zamenis Ricciola and Zacholus Ausiriacus of which there are numerous specimens in the Bonaparte collection 
belonging to the Academy, the nostrils open between two plates. 
