8 VENOMOUS SNAKES AND THE PHENOMENA OF THEIR VENOMS 
and very distinct from the narrow neck. Two loreals, one anterior to the other. 
Anal scutum divided, subcaudals in two series. Scales smooth and subequal. 
Coloration pale, with darker blotches. Chiefly Central American and Mexican 
genus, with one exceptional species which ranges within the United States north- 
wardly. All of the species are of moderate size, reaching a length of 3 feet and 
the thickness of a man’s forefinger. They live on lizards, young snakes, and 
batrachians. Their disposition is rather vicious. 
Trimorphodon lyrophanes Cope. ‘“‘ Jewsharp Snake.” 
Coloration, light gray; about twenty pairs of deep brown blotches along the back 
to base of tail; the tail also blotched; an irregular row of blotches on sides; 
ventral side white. Total length 2.5 to 3 feet. Found in southern Arizona and 
lower California. 
Trimorphodon upsilon Cope = Trimorphodon vilkinsonii Cope. 
(1) Top of head brown, with a small y-shaped mark; dorsal spots transverse 
diamonds, more or less transversely divided by paler spots; brown collar. 
(2) Top of head white, with 3 round black spots, a few transverse undivided 
black rhombs, with pale edges. 
Other species of this genus are Trimorphodon lambda Cope, Trimorphodon tau 
Cope, Trimorphodon collaris Cope. 
Genus SIBON Fitzinger. 
Sibon Fitzinger, Neue Class. Reptilien, 1826, 209. 
Heterurus Duméril and Bibron, Erp. gén., VIL, 1854, I170. 
Leptodira Giinther, Cat. Brit. Mus. Col. Snakes, 1858, 165. 
Eteirodipsas Jan, Elenco sist. ofidi, 1863, 105. 
An elongate grooved tooth on the posterior part of the maxillary bone; other 
teeth subequal. Pupil vertical. This genus is distinguished from Dipsas by the 
subdivided preanal plate; from Himantodes by the double scale pits, that genus 
having but one; from Trimorphodon by the equality of the solid maxillary teeth 
and the single loreal plate. In some of the species the head is less distinct and 
forms a gradual transition to the more fusiform types. Size moderate. Nine 
species constitute this genus and inhabit Central American and Mexican districts. 
One species (S. annulatum) extends its range throughout tropical South America 
and northward into southern Texas. 
Sibon septentrionale Kennicot. 
Body slender, with gradually tapering tail, which is about one-fifth of total length. 
Head ovoid, depressed, very wide, and swollen at temporal regions. Neck slender, 
about half as wide as head. Coloration of body light-yellowish ground with broad, 
lustrous, brownish-black half rings; abdominal surface uniformly light-yellowish. 
Oviparous. Southern portion of Texas, New Mexico, Panama, Arizona, Mexico. 
Other species of this genus are Sibon yucatanense Cope, Sibon annulatum' L.., 
Sibon personatum Cope, Sibon rhombiferum Ginther, Sibon frenatum Cope, Sibon 
nigrofasciatum Giinther, Sibon pacificum Cope. 
Genus SCOLECOPHIS Cope. 
Scolecophis zemulus Cope. 
Groove of posterior maxillary teeth shallow. Coloration of body exactly similar 
to Elaps fulvius. It is surrounded by wide black rings, broadly bordered with 
yellow and separated by red interspaces of twice their width. The scales of the 
red spaces have each a central black spot which is more distinct than in Elaps 
fulvius, on the anterior part of the body, above the sides; posteriorly they are weaker. 
The coloration of the head differs from Elaps fulvius in having merely a large black 
spot covering the parietal, superciliary, and frontal plates, and extending round 
the eye, but not reaching edge of lip. Muzzle and chin unspotted. The tail has 

1 Dipsas annulata Duméril and Bibron. Leptodra annulata Giinther. 
