_Leptodeira_ (in part), Guenther, Proc. Zool. Soc. London, pp. 317-318, 1860; Garman, Bull. Essex Inst., vol. 16, p. 23, January 9, 1884; Dunn, Proc. Nat. Acad. Sci., vol. 22, pp. 697-698, December, 1936; Duellman, Bull. Amer. Mus. Nat. Hist., vol. 114 (1), pp. 95-96, February 24, 1958. _Hypsiglena_ (in part), Cope, Bull. U. S. Nat. Mus., no. 32, p. 78, 1887; Guenther, Biologia Centrali-Americana, Reptilia, pp. 137-138, pl. 49, fig. A, October, 1894; Boulenger, Catalogue Snakes British Museum, vol. 2, p. 211, September 23, 1894; Mocquard, _in_ Dumeril and Bocourt, Mission Scientifique Mexique l'Amerique Centrale, vol. 3, p. 871, 1908; Amaral, Mem. Inst. Butantan, vol. 4, p. 183, May, 1930. _Pseudoleptodeira_ (in part) Taylor, Univ. Kansas Sci. Bull., vol. 25, no. 15, p. 343, June 1, 1938. _Type Species._--_Leptodeira discolor_ Guenther, Proc. Zool. Soc. London, pp. 317-318, 1860. _Diagnosis._--A xenodontine colubrid snake having a bifurcate hemipenis with a forked sulcus spermaticus, many longitudinal folds on basal portion, and small spines and calyces on distal part; 12 or 13 maxillary teeth followed by short diastema and two somewhat enlarged maxillary teeth lacking grooves; small parotid gland; normal colubrid skull; no hypapophyses on posterior vertebrae; elliptical pupils; two apical pits; smooth scales; normal colubrid head shields; divided anal; paired caudals. The generic name comes from the Greek Tantalos, a mythological character symbolic of eternal torment, and from the Greek ophis for snake. _Tantalophis discolor_ (Guenther) New comb. The synonymy for the species is indicated in the account of the genus. The description below of the species is based on an adult male from 6 miles southeast of Tamazulapam, Oaxaca, Mexico (University of Kansas Museum of Natural History No. 40143). _Scutellation._--Head shields normal; upper labials 7-7 (third and fourth entering orbit); lower labials 9-9 (1-4 in contact with anterior chin-shield, 4 and 5 in contact with posterior chin-shield); preoculars 1-1 and not in contact with frontal; postoculars 2-2; temporals 1-2-3, 1-2-3; nasals divided by a distinct groove below nostril and faint groove above; portion of rostral visible from above, one-third length of internasals; internasals pentagonal and one-half as long as prefrontals; parietal suture approximately as long as frontal; ventrals 178; anal divided; caudals 80. Scales in 21 rows at midbody and showing the following reduction: 2 + 3 (130) 8 + 9 (162) 21 --------------- 19 -------------- 17 (178) 2 + 3 (130) 8 + 9 (152)