brown and tan cross-bars. Specimens of Cnemidophorus sacki sacki of equal size from Guerrero, Morelos, and Puebla in the upper Balsas Basin have a tan dorsum with dark brown cross-bars. The localities in eastern Michoacán are intermediate geographically between the Tepalcatepec Valley and the known range of the nominal subspecies in the upper Balsas Basin. In characters of scutellation specimens from the east are intermediate between C. sacki sacki and C. sacki zweifeli in the Tepalcatepec Valley. However, in coloration the lizards from the east are like those from the Tepalcatepec Valley, but differ distinctly from the nominal subspecies. Therefore, the eastern series is referred to the subspecies C. sacki zweifeli.

Comparisons.—Four other species of Cnemidophorus occur in the Tepalcatepec Valley with Cnemidophorus sacki zweifeli. Of these, C. calidipes has a maximum snout-vent length of 79 mm., 66 to 86 dorsal granules, and a light brown dorsum with pale blue spots and vertical bars; C. communis communis has a maximum snout-vent length of 135 mm., 105 to 144 dorsal granules, and a greenish tan dorsum with yellow spots; C. deppei infernalis has a maximum snout-vent length of 84 mm., 91 to 120 dorsal granules, and a striped pattern throughout life; and C. lineatissimus exoristus has a maximum snout-vent length of 98 mm., 108 to 135 dorsal granules, and a middorsal yellow stripe and vertical bars on the flanks. Both calidipes and communis are like sacki in possessing four enlarged supraoculars and enlarged postantebrachials, whereas deppei and lineatissimus have three enlarged supraoculars and granular postantebrachials. Juveniles of calidipes and sacki are alike in coloration but different in the extent of the supraorbital semicircle-series. In calidipes the supraorbital semicircle-series usually are complete, whereas in sacki the series never extended anterior to the posterior edge of the frontal.