16 ; SYNOPSES AND DESCRIPTIONS, 
Long, slender; 
Scales in 23 (21—23) rows, ventrals 266 (+) 
biscutatum, 
Scales in 21 rows, ventrals 206—210 (+ ) 
var. latifasciatum. 
Moderate; 
Postmaxillary tooth longer, grooved ; 
Scales in 19—25 rows, ventrals 181—188 (+) 
annulatum. 
dorsal series broad transverse bands 
var. septentrionale. 
dorsal series of spots rather small 
torquatum. 
Postmaxillary teeth in continuous series, not grooved ; 
Scales in 19 rows; ventrals 179—182 (+) 
discolor. 
SIBoN BISCUTATUM. 
Dresas Biscutata Dum. Bibr., 1854, Erp. Gén. VIT, 1153. 
Long, slender, compressed; head distinct, broad oval, depressed, snout 
prominent, broad, rounded; tail moderate, tapering. Eye large, pupil erect. 
Mouth-cleft deep, slightly curved. Anterior maxillary teeth longer; pos- 
terior large, isolated, grooved. Head-shields nine, broad. Rostral broader 
than high. Nasal divided. Loreals two to four. Orbitals 2 to 3—2 to 3. 
10, fourth and fifth usually under the 
eye, the four preceding the last larger. Infralabials 11—13. Submentals 
Temporals irregular. Labials 9 
two pairs; posterior small, not in contact. Scales in 23 rows. Ventrals 
264 (+). Anal bifid. Subcaudals 94 (+) pairs. 
Light brown, punctulate, with broad transverse bands or rhombs of 
brown, which are paler in the center and separated by spaces about equal 
to their width. The bands become narrower toward the abdomen, at the 
edge of which there is an alternating series of spots. Abdomen sprinkled 
with brown; subcaudals with blotches. A light band across the head 
behind the internasals; another across the frontal passes through the eyes 
to the angle of the mouth. A V-shaped light spot on the vertex and a 
light collar behind the occiput. (From D. & B. and Jan.) Hab. Mexico 
and southward. 
