FAMILY COLUBERIDiE. 51 



GENUS HETERODON. Pal. de Beauvois. 



Teeth unequal ; the posterior maxillary teeth largest. Head triangular, pointed. Rostral 

 plate pyramidal, triangular, ridged above, and pointed at the tip. 



THE HOG-NOSED SNAKE. 



HeTERODON PLATYRHINOS. 



PLATE XIII. FIG. 28, A. Plates of the head. — (CABINET OF THE LYCEUM.) 



Heterodon a large nez. Latreille, Hist. Rept. Vol. 4, p. 32. 



Heterodon. Daud. Vol. 7, p. 153. 



Coluber heterodon. Say, Am. Jour. Vol. 1, p. 2G1. Harlan, Med. and Pbys. Res. p. 120. 



Heterodon platyrhinos. HoLBKooK, N. Am. Herpetology, Vol.2, p. 97, pi. 21. 



H. id. Stoeer, Mass. Rep. p. 231. Troost, Ann. Lye. Vol. 3, p. 183. 



Characteristics. Greyish tinged with yellowish, and a triple series of blackish blotches. 

 Dorsal series largest, bordered with black; lateral series smaller, and 

 irregularly rounded. A dark band through the eyes. Length two feet. 



Description. Body robust, and covered with oval-oblong carinate scales ; the two or three 

 .series next to the abdominal plates, smooth. The body tapers rather suddenly from the vent. 

 Tail short, one-sixtli of the total length, ending in an acute tip. Ventral scale divided. Head 

 large, triangular, flattened above, with a pointed snout. Teeth in the posterior part of the 

 jaw long, hollow, not perforated, and four in number. The plates cover but a small portion 

 of the head. Central plate irregularly six-sided, the lateral margins being longest, and the 

 anterior meeting at an obtuse angle ; supra-orbital oblong, broadest behind, and projecting over 

 the eye. Around the eye are arranged ten small orbital plates ; besides these, there are two 

 pair of anterior nasal plates, of which the superior are largest, the lower plate being behind the 

 posterior nasal plate, and furrowed in its centre. Nasal plates two on each side ; the anterior 

 lunated behind, the posterior excavated in front to complete the nostril. Occipital plates 

 triangular, with the apices truncated at their junction with the vertical plate. Frontal plate 

 uniting laterally with the anterior and posterior nasal plates ; between the frontal plates is a 

 long narrow azygous plate, ridged above, and uniting in a sub-imbricate manner on nearly the 

 centre of this plate with the rostral plate. Rostral plate triangular, upturned in front, with a 

 strong carina on its upper surface, and excavated beneath. Labial plates above eight on each 

 side of the lower jaw ; nineteen in all. Nostrils large, lateral, and near the rostrum. Eyes 

 large, prominent. Head in repose not much larger than the neck ; but when irritated, it 

 distends to twice its usual breadth, the summit becoming flattened. 



Color. Brassy yellow above, with three series of irregular subquadrate or rounded deep 

 chesnut, blackish or ash grey blotches, occasionally united on the posterior part of the body 

 and tail, forming rings ; the series on the sides much smaller, and alternating with the larger 

 ones. Summit of the head dark rufous, with irregular blotches and dots of dark brown. A 



