CROCODILIANS, LIZARDS, AND SNAKES. 953 



Pupil elliptic, erect. Head distinct, broad posteriorly, body cylindrical. 

 Cephalic shields normal. Two nasals, nostril between; oneloreal; two 

 preoculars and two postoculars. Scales smooth. Gastrosteges not 

 angnlated. Anal and subcaudal scntelLT3 divided. Tail not elongate. 



This genus includes four species of Central America, Mexico, and 

 parts of the United States adjacent to the latter. They are of small 

 size, and resemble considerably the more robust species of iSibon. 

 Their vertical pn])il indicates that they are of nocturnal habits. 



But one species enters the limits of the United States. 



HYPSIGLENA OCHRORHYNCHA Cope. 



Hypsiglena ochrorhynchns Cope, Proc. Acad. Nat. Sci. Phila., 1860, p. 246. 

 Hypsiglena chlorophwa Cope, Proc. Acad. Nat. Sci. Phila., 1860, p. 246. — Boulen- 

 GER, Cat. Suakes Brit. Mns., II, 1894, p. 209, 



Muzzle shortly conic; rostral plate prominent, encroaching a little on 

 the prefrontals. Nasal plates indistinctly separated, equal, their upper 

 and lower borders parallel. Loreal longer than high. Lower preocular 

 small, bounded anteriorly by the third upper labial. Eight upper 

 labials, fourth and fifth entering the orbit; sixth and seventh very 

 large. Vertical plate twice as long as broad ; lateral borders slightly 

 convergent. Superciliaries narrow ; oc- 

 cipitals as long as, or longer than, verti- 

 cal, and rounded posteriorly. Inferior 

 labials eleven, sixth largest. Geneials 

 two pairs, the posterior acute. Scales 

 in twenty-one rows. Gastrosteges, 1G8; 

 urosteges, 48 pairs. 



The upper surface light gray, with a Fig. 245. 



series of large brown spots, separated iiypsiglenaochrorhtnchaCope. 



by intervals of one scale wide. These ^ ^■^^ 



, x^ ^ J? . • ^ i. ' T_ Capo St. liucas, Lower California. 



spots are about forty eight m number, 



^ .7 7 C3t_ j^o_ 5„l^;j^ U.S.N. M. 



upon the body; they extend trans- 

 versely from the seventh to the lifteeuth rows of scales, and are three 

 or four scales in length. On the posterior part of the body they some- 

 times divide longitudinally, their moieties alternating or becoming con- 

 fluent into a zigzag band. Alternating with these on each side is a 

 series of small spots formed by the brown borders of scales of the fifth 

 and sixth rows. Another series of small spots oi)posite to the dorsal 

 row is formed by the shading of the adjacent borders of the fourth and 

 fifth rows with the same color. Many of the scales of the second row 

 are also tipped with brown. There is a large brown spot on each side 

 of the neck, sometimes confluent with an elongate central one, which 

 extends to the occipital plates. A brown stripe passes from the eye 

 to the neck spot, entirely covering the last upper labial. Top of the 

 head brownish gray, indistinctly spotted with pale brown. Labial 

 plate paler; frontals and rostral ochreous. Beneath yellowish white, 

 immaculate. 



