_Conophis lineatus_ (in part), Günther, Biologica Centrali-Americana, p. 165, March, 1895; Gaige _in_ Pearse, _et al._ Carnegie Inst. Washington Publ., 457:302, February 5, 1936. _Conophis lineaticeps_ Cope, Ann. Rept. U. S. Natl. Mus. for 1898, pp. 1094-95, 1900 (Substitute name for _Conophis vittatus_ Cope, 1861, _nec_ Peters, 1860). _Conophis lineatus concolor_, Smith, Journ. Washington Acad. Sci., 31:122-123, March 15, 1941; Proc. U. S. Natl. Mus., 92:395, November 5, 1942; Proc. U. S. Natl. Mus., 93:407, October 29, 1943; Smith and Taylor, Bull. U. S. Natl. Mus., 187:43, October 5, 1945; Univ. Kansas Sci. Bull., 33(pt. 2):352, March 20, 1950. _Types._--Two in the United States National Museum, no. 12368 (two specimens). Type locality: "Yucatán," restricted to Chichén Itzá, Yucatán, México by Smith and Taylor (1950:352). _Diagnosis._--Dark stripes either absent posterior to the nape, or present as a row of small spots on fourth or seventh scale-row; no dark stripe on first scale-row; eight supralabials having dark ventral margins. _Variation._--Forty-five specimens have 158 to 170 (163.7 ± 1.56) ventrals. Thirty-eight of these snakes having complete tails have 56 to 74 (66.7 ± 4.77) subcaudals; the number of ventrals plus subcaudals varies from 222 to 245 (230.6). In 45 specimens the reduction from 19 to 17 dorsal scales takes place between ventrals 89 and 114 (102.5 ± 5.57). Sexual dimorphism is evident in the number of subcaudals; 16 females have 56 to 65 (61.8), and 22 males have 68 to 74 (70.3) subcaudals. The longest specimen (USNM 46395) is a male from Chichén Itzá, Yucatán, having a body length of 893 mm., a tail length of 274 mm., and a total length of 1167 mm. A juvenile (AMNH 38833) from Chichén Itzá, Yucatán, has a body length of 194 mm., a tail length of 50 mm., and a total length of 244 mm. The venter is immaculate white or pale yellow and the dorsum of the body is immaculate pale gray to pale olive. Some specimens have small dark brown spots on the tips of the scales of the 4th or of the 7th row, but never on both. Only on the nape are spots present on both the 4th and the 7th rows; these spots are the posterior continuations of the dark stripes on the head and on many specimens do not reach the nape. Posterior to the place of scale reduction from 19 to 17 rows by the fusion of the 3rd and 4th rows of scales, the dark spots (when present) are on the 3rd or 6th row of scales. The coloration of juveniles is the same as that of adults. Color in life is thought not too different from that of preserved specimens, for notes on the color of living individuals (Neill and Allen, 1961:44) agree with what I have observed on preserved snakes.