APPENDIX F. REPTILES. 193 



but it extends to the Rocky mountains on the west, and far into Mexico 

 on the south. Its centre of distribution appears to be on the lower Rio 

 Grande. 



Plate III represents this species in natural size. 



III. HETERODON, Pal. de B. 



This genus is eminently characterized by the peculiarity of its snout, 

 which is terminated by a triangular plate recurved upwards ; hence the 

 popular appellation of hog-nose snake. Though perfectly harmless, they 

 ■exhibit a threatening appearance, when approached, in the flattening of 

 their head and violent hissings ; hence the names of blowing-viper, 

 spreading-adder, &o. Their body is short, stout, and the tail also short. 

 The head is broad and short. The dorsal scales are carinated, and ar- 

 ranged in 23-27 rows. The preanal or postabdominal scutella is bifid ; 

 a chain of small plates beneath the eye, completed above by the super- 

 ciliaries. There is a supplementary plate on the top of the head, be- 

 hind the prominent rostral, either in contact with the frontals, or sepa- 

 rated by smaller plates. The colors are light, with dorsal and lateral 

 darker blotches, or else brown, with dorsal transverse light bars ; some- 

 times entirely black. 



One species only was collected on the Red River exploration. Six 

 species are known to exist in the United States. 



4. Heterodon nasicus, B. & G. 



Zoology, PI. IV. 



Spec. char. — Vertical plate broader than long. Rostral excessively 

 broad and high. Azygos plate surrounded behind and on the sides by 

 many small plates (12-15.) A second loral. Labials short and exces- 

 sively high. Dorsal rows of scales 23, exterior alone smooth. A dorsal 

 series of about 50 blotches, with four or five other series on each side. 

 Body beneath, black. A narrow white line, across the middle of the 

 superciliaries ; a second behind the rostral. A broad dark patch from 

 the eye to the angle of the mouth, crossing the two postlabials. 



Stn. — Heterodon nasicus, B. & G. Reptiles in Stansbury's Expl. 

 Valley of Great Salt Lake, 1852, 352.— B. & G. Cat. N. Amer. 

 Rept. I, 1853, 61. 

 13 



