24 SYNOPSES AND DESCRIPTIONS. 
much faded, and shades into the olive beneath. Skin between the scales 
black. Short white lines to be seen on stretching the skin. Specimens 
from the Mississippi Valley show black spots in the brown of the flank. 
A vertical spot of yellow on the anteorbital. Dark color of the head 
extending to the rostral and upper labials. — A pair of small yellow spots 
near the inner margins of the occipitals. Closely allied to Z. sirtalis. 
Valley of the Mississippi and eastward. 
var. PROXIMUS. 
Stouter. Ventrals 168—178. Subcaudals 100—108. Mississippi Val- 
ley to Mexico. 
TROPIDONOTUS SIRTALIS, pl. LTT, fig. 3. 
Cotuser strraxis Linné, 1758, Syst. Nat., ed. X, 222; ed. XII, 1766, p. 383. 
Troprponotus sirrauis Holbrook, 1842, N. A. Herp. IV, 41, pl. XI. 
Young slender, old moderately stout; head distinct, broad behind, nar- 
row in front, flat on the crown; tail medium, slender posteriorly, one 
fourth to one fifth of the total length. Nine head-shields. Vertical hex- 
angular. Rostral broader than high, Nasal in two parts, nostril between 
—in anterior portion. Loreal quadrangular. One anteorbital. Postor- 
bitals 5—4. Eye large, over the third and fourth or fourth and fifth 
labials. Mouth-cleft deep, curved. Labials 7 or 8, antepenultimate largest. 
Infralabials 10. Submentals two pairs, hinder larger. Scales keeled 
in 17—21 rows, dorsal narrow, outer broad. Ventrals broad 140—155 
(140—180 with the varieties). Subcaudals 50 
Brown above, varying from light ashy to very dark; olive beneath. A 
90 pairs. 
dorsal and two lateral narrow lines of yellow, sometimes faded or oblit- 
erated. In the brown space between the yellow lines on the flank are two 
series of quadrate alternating spots; sometimes the upper of these forms 
a band (var. collaris), and in cases the spots of the lower are joined to it 
(var. pickeringii). A brown band on the outer row (sometimes obsolete), 
with or without a series of spots. Black spots on the base near the 
extremities of each ventral are visible on bending the body. When the 
skin is stretched numerous short white lines are to be seen on the flanks 
of most specimens, A small yellow spot near the inner margin of each 
parietal shield, Chin and throat lighter colored, yellowish. Labials more 
or less bordered with black. Kentucky specimens show a light collar 
extending toward the occiput around the angle of the jaw, behind which 
