CROCODILIANS, LIZARDS, AND SNAKES. 819 



produced slightly between the postnasal and the loreal, on the sides of 

 the head. Frontal subpentagoual, much elongated, tapering posteriorly 

 without being pointed. Parietals elongated, posteriorly truncated, 

 sides rounded. Prenasal larger, subtrapezoidal ; postnasal subquad- 

 rangnlar; nostril situated at the anteroposterior angle of the postnasal. 

 Loreal subtriangular, base in a horizontal line with the head; apex 

 upwards produced between the postfrontal and the upper anteorbital. 

 Oculars 2-2 or 3-2. Upper anteorbital large, angular, produced to the 

 upper surface of the head between the superciliaries and postfroutaLs. 

 Inferior anteorbitals small and quadrangular, lowest situated on the 

 commissure between the fourth and fifth labials. Postorbitals angular, 

 equal in size. Two ijretemporals, shields somewhat larger than rest, 

 which are scarcely larger than the scales. Mouth deeply cleft, undu- 

 lating. Upper labials eight; seventh largest, the three anterior ones 

 comparatively small. Lower labials not conspicuous, ten in number, 

 fifth largest, the three posterior ones scarcely to be distinguished from 

 the scales. Posterior pair of mental scutellse much smaller than the 

 anterior, extending to the middle of the fifth inferior labial. Sym- 

 physeal plate very small. 



Body subcylindrical, elongated, tail subconical, tapering, forming 

 about the one-fourth of the total length. Scales elliptical, disposed in 

 seventeen rows; outer row somewhat broader, the rest slightly dimin- 

 ishing towards the dorsal region. 



Surface of head brown. An ochraceous vitta extends from the occiput 

 to near the end of the tail, embracing anteriorly three rows of scales, 

 and posteriorly one row, and two adjoining halves to opposite the anus; 

 on the tail it covers two half scales. On each side of this a brown 

 vitta runs parallel, and covers the same number of scales anteriorly 

 and posteriorly, except on the tail, where it is narrower, and embraces 

 only half a scale. The auterio-inferior margin of the scales in the 

 black vitta is yellowish green. The remaining portion of the flanks, 

 embracing four rows of scales, and the extremities of the scutelhe, is 

 uniform yellowish green, with the bases of the scales blackish, as is 

 also the skin. The abdomen is uniform dull yellow. 



Sonora ; gastrostegea, 180 + 1 ; urosteges, 97 ; total length, 28J iuches ; tail, 7i inches. 



Considerable variations are presented by this species. Thus in four 

 specimens (Cat. Nos. 4673, 4470, 14004, 17175) a narrow brown band 

 extends along the fourth row of scales, in addition to the usual one on 

 each side of the median line. In Cat. Nos. 4470, 2082 the superior 

 stripe is partially broken into spots. In Cat. No. 9001 the bands are 

 obsolete, being represented by blackish shades at the bases of the 

 scales. Several specimens (Cat. Nos. 2082, 9101, 5347, 12638, 13811, 

 16339) have a small loreal below the usual one. In five (Cat. Xos. 2082, 

 4470, 9101, 13811, 16339) a second inferior ocular is formed from the sum- 

 mit of the fourth superior labial plate, so that the fifth only enters the 

 orbit. On a specimen of this kind was proposed the Phimothyra hexalepis, 



