In the arid lowlands of the Tepalcatepec Valley and presumably also in the scrub forest of the coastal lowlands, this is an abundant snake, which is active only at night. Usually snakes of this species are found on the ground, but one large individual was observed at night in a low tree. That individual defied capture by widely opening its mouth and striking repeatedly at the collector. The excreta of one specimen contained feathers of an unidentified species of bird. ~Trimorphodon latifascia~ Peters _Trimorphodon biscutata latifascia_ Peters, Monats. Akad. Wiss. Berlin, p. 877, 1869.--Puebla, México. Type locality restricted to Izúcar de Matamoros, Puebla, México, by Smith and Taylor (1950a:341). _Trimorphodon latifascia_. Taylor, Univ. Kansas Sci. Bull., 25:364, July 10, 1939. Apatzingán (5); Casada Tzararacua; Coalcomán (2); Lombardia; 14 km. S of Lombardia; Nueva Italia; San Salvador. In Michoacán this species has been collected in semi-arid habitats at elevations from 300 to 1430 meters in the Tepalcatepec Valley and lower slopes of the Cordillera Volcánica. In this area it occurs sympatrically with _Trimorphodon biscutatus biscutatus_. In life, adults have a pale tan dorsal ground color and rich chocolate brown cross-bands; the eye is pale grayish tan. A juvenile from Coalcomán has black cross-bands on a pale grayish tan ground color. As stated by Schmidt and Shannon (1947:83) and Peters (1954:32), the type specimen of _Trimorphodon fasciolata_ Smith from Cascada Tzararacua is indistinguishable from specimens of _Trimorphodon latifascia_. Seven males have 209 to 223 (216.5) ventrals; one female has 227 ventrals. The number of dark cross-bands on the body varies from 12 to 16 (13.5). The relationships of this species are with _Trimorphodon tau_ on the Mexican Plateau. In fact, additional specimens from the headwaters of the Tepalcatepec Valley and the lower slopes of the Mexican Plateau in eastern Michoacán and adjacent Jalisco may show that the two are conspecific. _Trimorphodon latifascia_ differs from _tau_ in having fewer dark cross-bands on the body and in lacking an interocular bar. ~Trimorphodon tau~ Cope _Trimorphodon tau_ Cope, Proc. Amer. Philos. Soc., 11:151, 1869.--Quiotepec, Oaxaca, México. Emiliano Zapata (2); between Morelia and Ciudad Hidalgo; Tacícuaro; Tangamandapio.