This species is known only from the low areas of the Balsas-Tepalcatepec Basin between elevations of 200 and 510 meters. It is commonly found in the open arid tropical scrub forest dominated by _Prosopsis_ sp., _Apoplanesia paniculata_, and _Cercidium plurifoliolatum_. Continued collecting in the Tepalcatepec Valley has borne out the suggestions of Duellman and Duellman (1959) concerning the distribution and abundance of this lizard. Also, continued collecting in Colima and on the Pacific coast has failed to reveal the presence of _Enyaliosaurus_ there. ~Phrynosoma asio~ Cope _Phrynosoma asio_ Cope, Proc. Acad. Nat. Sci. Philadelphia, 16:178, September 30, 1864.--Colima, Colima, México. Apatzingán (4); San Salvador. In Michoacán this species has been obtained only in the Tepalcatepec Valley and on the northern slopes of the Sierra de Coalcomán between 300 and 700 meters. Apparently the lizard is absent from the coastal lowlands of Michoacán and Guerrero. The distribution of this species, therefore, is discontinuous. One population inhabits the lowlands of Colima and the Balsas-Tepalcatepec Basin inland to northern Guerrero and Morelos; a southern population inhabits the Plains of Tehuantepec in Oaxaca. A juvenile from Apatzingán (USNM 47739) has a snout-vent length of 40.0 mm. and a tail length of 19.5 mm. ~Sceloporus aeneus aeneus~ Wiegmann _Sceloporus aeneus_ Wiegmann, Isis von Oken, 21:370, 1828.--México. Type locality restricted to Tres Cumbres, Morelos, México, by Smith and Taylor (1950b:137). _Sceloporus aeneus aeneus_, Smith, Occ. Pap. Mus. Zool. Univ. Michigan, 361:6, December 15, 1937. Angahuan; Araparicuaro (2); Capácuaro (2); Carapan (11); Cherán (11); 18 km. WNW of Ciudad Hidalgo (10); Cuseño Station; Jeráhuaro; Los Conejos (36); Macho de Agua (7); Opopeo; Paracho (2); Pátzcuaro (4); Pino Gordo; 18 km. W of Quiroga (2); Tancítaro (49); Uruapan (14); 16 km. NW of Zacapu (5); between Zacapu and Zamora (2); 13 km. E of Zinapécuaro; 14 km. SE of Zitácuaro (14). This small terrestrial species inhabits the pine and fir forests of the Cordillera Volcánica between elevations of 1850 and 3100 meters; apparently it is absent from the Sierra de Coalcomán. It seems to prefer rather open coniferous forests in which there is a more or less continuous cover of grasses on the ground. On warm sunny days the lizards can be observed scurrying about in the grass; in the early hours of the day, or on cold days, they are found beneath stones, logs, or dead clumps of bunch grass. ~Sceloporus asper~ Boulenger _Sceloporus asper_ Boulenger, Proc. Zool. Soc. London, 1897:497, October, 1897.--La Cumbre de los Arrastrados, Jalisco, México. Apatzingán (3); 10 km. E of Dos Aguas; Uruapan (41).