The supposed differences in scutellation between _L. bicolor_ and _L. sumichrasti_ have been questioned by Woodbury and Woodbury (1944:360); these authors treated _L. sumichrasti_ as a subspecies of _L. bicolor_. As pointed out by Zweifel (1959b:5), such an arrangement is not tenable, for, although individuals with each kind of color pattern have not been collected together at any one locality, the over-all geographic picture is one of sympatric distribution. Only snakes having the coloration of _L. sumichrasti_ have been collected in the Balsas-Tepalcatepec Basin. I agree with Zweifel (_loc. cit._) that on the basis of morphological similarities and sympatric distribution, _L. bicolor_ and _L. sumichrasti_ seem to be dimorphic phases of the same species, showing no more striking differences in coloration than _Lampropeltis getulus californiae_, a now classical example of pattern dimorphism in snakes. In Michoacán, as in other parts of its range, _Loxocemus bicolor_ inhabits arid scrub forest environments at low elevations. ~Boa constrictor imperator~ Daudin _Boa imperator_ Daudin, Hist. nat.... des reptiles, 5:150, 1803.--México. Type locality restricted to Córdoba, Veracruz, México, by Smith and Taylor (1950a:347). _Boa constrictor imperator_, Forcart, Herpetologica, 7:199, December 31, 1951. Apatzingán (4); Coalcomán; El Sabino (2); La Placita; La Playa (2); Lombardia; Nueva Italia (2); Río Cachán; Río Marquez, 13 km. SE of Nueva Italia; Río Nexpa; Volcán Jorullo. These specimens have come from a variety of habitats from elevations of less than 1,000 meters. The species seems to be equally abundant in the broad-leafed semi-deciduous forests of the coastal foothills and in the arid Tepalcatepec Valley. In the latter area most of the specimens were collected at night. ~Coniophanes fissidens dispersus~ Smith _Coniophanes fissidens dispersus_ Smith, Proc. U. S. Natl. Mus., 91:106, November 13, 1941.--El Limoncito, Guerrero, México. Arteaga. Further collecting in southern Michoacán has failed to add additional material of this species, which is known in the state from the one specimen collected by Gadow in 1908. The species possibly ranges throughout the coastal foothills of the Sierra de Coalcomán. Peters (1954:21) described the specimen from Arteaga. ~Coniophanes lateritius lateritius~ Cope _Coniophanes lateritius_ Cope, Proc. Acad. Nat. Sci. Philadelphia, 13:524, March 31, 1862.--Guadalajara, Jalisco, México. _Coniophanes lateritius lateritius_, Smith and Grant, Herpetologica, 14:20, April 25, 1958. Nineteen km. S of Arteaga.