28. COLUBER 675 
markings on the rest of the underside are very dense, leav- 
ing only a pale line on the angle of the belly, or are con- 
densed into two fairly distinct parallel longitudinal bands 
with a pale zoue down the middle of the body. 
Wength tonanussss ie ee ee 190 
denpthyor tare se ee 360 
Distribution—This snake has been found only on Clar- 
ion Island of the Revilla Gigedo group, off the western 
coast of Mexico. 
147. Coluber semilineatus (Cope) 
Sonoran Racer 
Plate 67 
Bascanium teniatum laterale YaARRow, Surv. W. tooth Merid., Vol. V, 
1875, p- 543 (part). 
Bascanion semilineatum Cope, Proc. U. S. Nat. Mus., Vol. 14, 1892, 
p- 626 (type locality, Colorado River and Camp Grant, Arizona); 
Van Densurcy, Proc. Cal. Acad. Sci., Ser. 2, Vol. 6, 1896, p. 3473 
Van Densurcu, Proc. Acad. Nat. Sci. Phila., 1897, p. 463; STEJ- 
NEGER, Proc. U. S. Nat. Mus., Vol. XXV, 1902, p. 155; STONE, 
Proc. Acad. Nat. Sci. Phila., 1911, p. 231; Van DenBurcH & 
Stevin, Proc. Cal. Acad. Sci., Ser. 4, Vol. 3, 1913, p- 417. 
Zamenis semilineatus GinTHER, Biol. Centrali-Amer., Rept., 1894, p. 
121, pl. XLVI, fig. A; Cope, Report U. S. Nat. Mus., for 1898, 
1900, p. 805, fig. 417. 
Coluber semilineatus STEJNEGER & Barpour, Check List N. Amer. Amph. 
Rept., 1917, p. 80. 
Description—Head long, with flattened top, and nar- 
row, rounded snout. Rostral plate large, high, hollowed 
below, and bounded behind by internasal, anterior nasal, and 
first labial plates. Plates on top of head are a pair of inter- 
nasals, a pair of much larger prefrontals, supraocular and 
part of upper preocular of each side, long frontal, and pair 
of large parietals. Anterior and posterior nasals distinct. 
