198 KEPTILIA: OPHIDIA. — XXVIII. 



presses and expands the head, hissing and threatening, but it is 

 perfectly harmless. (TrXariJt, flat ; pi's, nose.) 

 aa. Vertical plate encircled by 5 to 10 small plates. 



576. H. simus (L.). Hog-nosed Snake. Dorsal blotches 

 about 35 ; ground color usually pale yellowish brown ; vertical 

 plate much longer than occipitals, broader than long. V. P. 115 to 

 1 50. Scales usually 25. 111. and Wis. to S. C, chiefly S. (Lat., 

 flat-nosed.) 



Family CXI. BLAPIDjSJ. (The Harlequin Snakes.) 



Venomous snakes, provided with two or more permanently erect, 

 perforated fangs in the upper jaw, and usually a series of smaller 

 teeth behind them; scales not keeled; head usually quadrangular, 

 with flat crown and short muzzle ; no loral plate. Genera 3, species 

 about 20, chiefly East Indian, a few inhabiting the warmer parts of 

 America. 



a. Anal plate entire; sub-caudal plates two-rowed; two nasal plates; inter- 

 nasal plate touching the nasal laterally Elaps, 289. 



289. ELAFS Schneider. (Old name of some snake.) 



577. E. fulvius (L.). Bead Snake. Jet black, with about 

 17 broad crimson rings, each bordered with yellow, and spotted 

 below with black; a yellow occipital band; tail with yellow rings. 

 V. P. 200 to 215. U. 32. Scales, 15 rows. L. 30. Xa. to Ark. 

 and S. A beautiful snake, apparently harmless, although provided 

 with venom-fangs. Resembles Lampr. doliatus. (Lat., reddish- 

 yellow.) 



Family CXII. CROTALID..^. (The Rattlesnakes.) 



Maxillary vertical, without solid teeth, but provided with long, 

 erectile, perforated poison-fang on each side in front ; a deep pit 

 between eye and nostril, extending into the excavated maxillary. 

 Body stout ; head large, flat, triangular, on a slender neck ; pupil 

 elliptical, placed vertically. Tail usually provided with a rattle 

 composed of horny rings, modified scales. Subcaudal plates gen- 

 erally undivided, at least anteriorly. Scales keeled, in all our 

 species; anal plate entire. Genera 12; species about 60, all Ameri- 

 can, renowned for their venom. All are viviparous. 



a. Tail short, without rattle, endinji; in a horny point ; top of head with about 

 8 symmetrical plates arranged around the vertical plate ; tail not pre- 

 hensile Agkisteodon, 290. 



aa. Tail with a rattle. 

 b. Top of head with about 8 plates symmetrically arranged ; rattle small. 



SiSTRURUS, 291. 

 hh. Top of head covered with small scales; rattle large. Crotalus, 292. 



