1901.] NATURAL SCIENCES OF PHILADELrillA. 89 



occasionally a small post-nasal below; scales keeled, with two pits, 

 in 23-25 rows; anal divided. 



Hab. — Norch America. 



The "sand snakes," "hog-nosed snakes," or "blowing 

 vipers," as they are variously called, are able to expand and flatten 

 the anterior portion of the body when alarmed, and thereby to 

 assume a threatening aspect, as in the cobras, but they are abso- 

 lutely harmless. 



Key to the Species. 



a. — Rostral narrower than space between eyes: 

 No scales between prefrontals; size larger, 



1. H. platyrhlnns. 

 Prefrontals separated by scales; size smaller, 2. B. simus. 

 b. — Rostral as broad as space between eyes: 



Prefrontals and interuasals separated by scales, 



3. H. nasicus. 



Heterodon platyrhinus Latreillo. 



I. c. 32 ; R. plati/rhinos, IT. cognatus, H. nujer and //. atmodes B. 

 and G., I. c, 51-57 ; //. plnty'r/unus Cope, I. c, 643, and Rep. Nat. 

 Mus., 761; BouL, I. c, II, 151. 



Largest of the genus; maxillary teeth 11-12, the last two much 

 enlarged and separated by a wide interval; 1, sometimes 2, small 

 azygous plates behind the rostral, separating internasals; usually 

 without small plates between the prefrontals; frontal a little longer 

 than broad; 9-11 scales in the orbital ring, in addition to the 

 supraoculars; upper labials 8 (9); temporals 4 (3)-5; 1 jtair of 

 chin shields; scales usually in 25 rows (occ. 23); ventrals 120- 

 150; subcaudals 37-60. Length 810 mm. (tail 153). 



Color variable, sometimes entirely black above; usually brown, 

 reddish brown or yellow, with a dorsal series of dark brown or 

 black spots, separated by narrow interspaces, one and a half or 

 two scales wide ; a lateral alternating series of small dark blotches, 

 and sometimes ti'aces of a third; belly greenish white, yellowish 

 or reddish, often clouded with dusky; two dark blotches on the 

 nape, a band across the prefrontals and an oblique streak behind 

 the eye. 



Hab. — New Jersey west to the Missouri river, and south to 

 Florida and Texas. 



