I 
46 Transactions Texas Academy of Science. 
talus atrox lie in the dorsal blotches, being disposed in subqnadrate spots 
instead of snbrhomboids ; the intervals thns forming bands across the 
back perpendicular to the longitudinal axis. This tendency to assume 
a subquadrangular pattern has broken up the chain work into isolated 
portions, as in Coluber eximus or Crotalophorus tergiminus ( Sistrurus 
catenatus) . The intervals of the dorsal blotches are wide and darker in 
the middle, while in Crotalus atrox they are narrow, not linear, and uni- 
color. The sides of the head present the usual light stripe from the 
posterior extremity of the superciliary ; and passes, however, to the angle 
of the jaw on the neck, along the second row of scales, above the labials. 
A second stripe passes in front of the eye to the labials, widening there. 
A small light vertical bar is seen below the pit and another on the outer 
edge of the rostral. On the superciliaries are seen two light transverse 
lines inclosing a space nearly one-third of the whole surface. In Crota- 
lus atrox there is a single median line. Sometimes, as in Crotalus atrox , 
the single blotches on the nape are replaced by two elongated ones par- 
allel to each other.” 
(Stejeneger, “Poisonous Snakes of North America”). 
GEOGRAPHICAL DISTRIBUTION. 
Quoting from “Poisonous Snakes of North America” (Dr. Stejene- 
ger), pages 443 and 444: “While in northwestern Texas it is recorded 
from between the main forks of the Brazos Eiver and on the Llano 
Estacado as far south as Canon Blanco.” 
“Further west Captain Pope collected specimens at the Pecos Eiver 
near the thirty-second parallel.” ( Cope, Zool. Pos. Texas, p. 24 ; Proc. 
Phila. Acad., 1892, p. 336.) 
HABITS. 
Again quoting Stejneger, “Poisonous Snakes of North America,” p. 
444: “The prairie rattlesnake being one of the smaller species, as it 
seldom reaches a length of over four feet with a proportionately slender 
body, does not seem to be a very dangerous snake. Dr. Allen, as referred 
to above (Lknion Pacific Eailroad Expedition), found it so common in 
the region visited by the expedition that several hundred were killed by 
the different members, yet the only casualty resulting from it was one 
horse bitten. On the expedition of 1872, not less than two thousand 
were killed, and not a man nor an animal was bitten. Allen also com- 
ments upon the fact that they were found abroad quite late in the 
season, as they were met with quite frequently after several severe frosts 
had occurred. During July two pairs were found in coitu, indicating 
the season at which they pair. Dr. 0. P. Hay (Proc. U. S. Nat. Museum, 
