SYNOPSES AND DESCRIPTIONS. 51 



PlTYOPHIS. 



Holhmok, 1842, N. A. fferp. TV, 7. 



Long, moderately stout, compressed; head distinct from the neck, sub- 

 conical, broad posteriorly, pointed at the muzzle; tail rather short. Eye 

 moderate, pupil round. Teeth equal, smooth. Crown-shields nine to 

 eleven. Prefrontals one to two pairs. Nasal divided. A loreal, rarely 

 suppressed. One to two preoculars. Postoculars two to five. Scales 

 keeled, in 27 to 35 rows. The individual variation is very great in 

 specimens belonging to species of this genus, particularly so in those of 

 the Rocky Mountains, 



PlTYOPHIS MELANOLEUCUS. 



Collt.er melanoleitcus Ddudin, 17'J'.\ IIL4. Nat. Rept. VI, 409. 

 PiTYorms MELANOLEUcrs Ilulbmok, 1842, N. A. Ila-p. IV, }J. 7, pi. I. 



Long, moderately stout, slightly compressed; head moderate, distinct 

 from the neck, appearing subquadrangular when viewed from the front, 

 narrowing forward, conical or pointed, crown slightly convex, very broad 

 behind; snout prominent; tail short, rather less than one seventh of the 

 total, stout, tapering. Eye moderate, pupil round. Mouth-cleft deep, 

 slightly curving. Crown-shields more or less irregular, commonly two 

 pairs of prefrontals. Rostral very prominent, narrow, swollen, extending 

 on the upper surface of the head, between the internasals. Internasals 

 short, wide. Outer prefrontals extending on the side of the face to the 

 loreal, inner narrow posteriorly. Fi'ontal broad anteriorly. Supraciliarics 

 prominent, broadening backward. Parietals large, nearly as wide as long. 

 Nasal in two parts, nostril between. Loreal small, sometimes united with 

 adjacent plates. One preocular. Postoculars three to four. Two or more 

 temporals in contact with the postoculars, sometimes broken into small 

 scales. Labials eight, fourth below the eye, fifth under the postorbital, 

 seventh largest. Infralabials thirteen to fourteen, fifth and seventh large, 

 hinder very small. A pair of large submentals, followed by a pair of 

 .smaller ones, which are separated by a pair of small plates. Scales 

 lozenge-shaped, usually in 27 or 29 rows (ranging in the different varie- 

 ties from 27 to 35), outer broad, lateral smooth, vertebral keeled. Ven- 

 trals 212 — 216, broad. Anal entire. Subcaudals 58 to 60 pairs. 



Color whitish, tinged with red on the back, with a dorsal series of large 

 spots of dark brown or black — becoming bands posteriorly — thirty or more 



