AMPHIBIA AND REPTILIA OF COLORADO 95 



Genus HETERODON Latreille 



Heterodon Latreille, Hist. Nat. Reptiles, Vol. IV, p. 32, 1799. 



Anal plate divided; scales keeled, in 23 or 25 rows; rostral plate 

 large, produced, upturned and recurved, producing a ''snout" at the 

 end of the head; a ring of scales around each eye, of which three or 

 four are in front of the eye; posterior maxillary teeth much longer 

 than those in front; large, thick-bodied snakes. 



The snakes of this genus are known as the Hog-nosed Snakes, and 

 incorrectly as "Spreading Vipers and Adders." The last two names 

 are the result of the ability of these snakes to expand the anterior 

 portion of the body when disturbed so as to resemble somewhat the 

 Asiatic Cobra. They are, however, harmless. When disturbed the 

 Hog-nosed Snakes make a very elaborate show of fight. The snake 

 expands the body just back of the head and strikes vigorously and 

 viciously, although it rarely bites even if opportunity be offered. If 

 these demonstrations are not sufficient the snake may feign death, 

 suddenly, by dropping over on its back. Hog-nosed Snakes are often 

 confused with rattlesnakes by those unfamiliar with them. They 

 feed for the most part on toads and frogs. 



The three species of this genus are found only in North America. 

 They are oviparous. 



Heterodon nasicus Baird and Girard 



Western Hog-Nosed Snake (Figures 28, 2g, 30 and 31) 



Heterodon nasicus Baird and Girard, Cat. N. Am. Reptiles, Pt. I, p. 61, 1853. 



Heterodon nasicus — Baird, Pacific R.R. Survey, Vol. X, Pt. V, No. 3, p. 19, 

 1857 (No. 1263, Rocky Mountains). 



Heterodon simus nasicus — Yarrow, Wheeler Survey, Vol. V, pp. 555-556, 1875 

 (Denver and Pueblo, Colo.); Yarrow, U.S.N.M., Bull. 24, p. 141, 1882 (Ft> 

 Lyon, Colo.). 



Heterodon nasicus nasicus — Cope, Rept. U.S.N.M., p. 777, 1898 (Ft. Lyon, 

 Colo.). 



Dorsal scales keeled, in 23 rows; superior labials, 8; inferior 

 labials, 10; 10 or 1 1 scales around the eye; several small scales between 

 the prefrontals and the internasals; ventrals, 125 to 150; tail one- 



