synopses and descriptions. 45 



Coluber mexicanus. 



Zamenis mexicanus D. <£ B., 1854, Erp. Gen., 695. 



Long, slender, belly broad ; head distinct from neck, elongate, depressed, 

 crown flat, sides concave at the eye; tail near one third of the total, 

 slender, tapering regularly. Mouth-cleft deep, sinuous. Eye moderately 

 large, pupil round. Crown-shields normal. Rostral prominent, higher 

 than wide, bent back between the internasals in an acute angle. Pre- 

 frontals broader than long. Frontal long, sides concave. Supraoiliaries 

 large, prominent. Nasal divided. Loreal present. Preoculars large, con- 

 siderably in contact with the anterior angles of the frontal. Two postoc- 

 ulars, lower resting on the sixth labial. Temporals 2-1-2+2. Labials nine, 

 fourth, fifth, and sixth in the orbit, hinder four larger. Infralabials ten, 

 sixth largest. Submentals two pairs, nearly equal. Scales smooth, in 

 17 rows, dorsal narrow, lateral as broad as long. Yentrals 182. Anal 

 bifid. Subcaudals 128 pairs. 



Light brownish or yellowish-brown. Posteriorly with four black bands 

 on the dorsal rows, each of the width of two scales, separated on the flank 

 by a space of equal width and by the median row of scales on the back. 

 Forward the bands are broken up and each scale of the dorsal rows is 

 more or less marked with black. The first band occupies a portion of 

 the outer row and all of the second. Anteriorly the back is crossed by 

 transverse bands of brown, the first of which crosses the head just behind 

 the parietals and meets the bands from the eye. Crown-shields broadly 

 margined with brown. Parietals. divided longitudinally by a band, a dot 

 of brown on the yellow portion of each near the middle. Total length 

 31 J inches; tail lOf inches. San Bias, Jalisco, Mexico. 



Coluber spinalis. 



Masticopiiis spinalis Peters, 1866, Monatsber. Berl. Akad., 91. 



Very long and slender; head twice as long as broad, snout prominent, 

 rounded; tail near one fourth of the total. Posterior maxillary tooth 

 longer, smooth. Crown-shields nine. Prefrontals broader than long, not 

 longer than the internasals. Nasal in two parts, nostril between, above 

 the middle. Loreal trapezoidal, longer than broad. Two preocufers; 

 upper large; lower small, in a notch between the third and fourth labials. 

 Frontal long, broad and blunt -angled in front, concave at the sides. 

 Parietals hardly longer than the frontal Supraciliaries narrow in front. 



