As noted by Peters (1954:21), this species was not recorded from Michoacán by Smith and Taylor (1945:27), but Gadow (1930:30) collected a specimen at La Orilla in 1908. This specimen (BMNH 1914.1.28.124) is a male having 235 ventrals and 47 caudals, a dark brown dorsum, and cream-colored labials and venter. The anterior chin-shields are considerably longer than the scales bordering the chin-shields. In these characters this specimen agrees with the diagnosis of Loxocemus bicolor given by Taylor (1940c:447), who revived Loxocemus sumichrasti Bocourt. Of the six specimens from Apatzingán in the Tepalcatepec Valley, three males have 243 to 253 (246.6) ventrals and 44 to 45 (44.3) caudals; three females have 238 to 247 (244.0) ventrals and 42 to 44 (43.0) caudals. Certain characters of scutellation utilized by Taylor for separating L. bicolor and L. sumichrasti are inconsistent in this series. The chin-shields are longer than the adjacent scales, like those illustrated in L. bicolor by Taylor (op. cit., fig. 1). The relative lengths of the prefrontal and internasal sutures are subequal, or the prefrontal suture is slightly longer. Thus, in these characters of scutellation these snakes are like L. bicolor, but in coloration they are like L. sumichrasti; the dorsal color in life was an iridescent dark bluish gray, and the belly was pale gray or bluish gray.
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.