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Show 1906.] IN MEXICAN LIZARDS. 337 Forearm, posterior surface, always covered with much-enlarged scutes, the largest in the middle, reaching towards the wrist; on the elbow continuous with the 6th or 5th, rarely with the 4th row of humeral scales. Femur : Mostly with 5 very regular rows, rarely with 6, which are then rather irregularly disposed ; the three largest rows reach the knee as in C. deppei. One specimen, 60 mm., has 7 unmistakable rows; another of 50 m m . has 7 incomplete right and 6 regular rows on the left thigh. Tibia covered with 2 very large rows, with a third smaller row on the fibular side, i. e. the side turned towards the tail. Preanal isthmus short, with only one or two transverse rows of small scales between the ventrals and the preanal plates. The detail is very variable. Femoral pores: From 15/17 once, to 21/21 once. Usually with 17, 18, or 19 rows; 20 did not occur. The solitary occurrence of 21/21 refers to a specimen 60 m m . in length; the only one possessing 7 femoral rows of scales, and further distinguished by the almost complete absence of pale spots in the black dorsal fields. Coloration and pattern.- Under parts of young white and mother-of-pearl; immature specimens have the chest and abdomen suffused with pale bluish, and dark pigment appears in the basal portion of the scales. In the adult, throat, collar, thighs, and tail are yellowish white; chest and flanks, less so the belly, are mottled blue-black, the edges of the scales remaining whitish. Upper surface (figs. 68 & 76). The young start with 6 sharp white stripes, with single or double rows of pale spots in the fields, and also with a row of white spots in the middle line. In specimens of about 70 m m . the stripes have become dull to pale grey, with small white dots in the dulled stripes. Field-spots brown, yellow, or brown-yellow, and more numerous, and their double rows in each field become confluent. Ultimately the stripes are lost, remaining traceable longest on the neck; the whole back is covered with numerous cross-bars or vermiculations of deep black and vivid yellow, or orange, with many white spots on the thighs, legs, and rump. In some beautiful specimens the tiger-bar pattern is complete, there being about 30 black cross-bars from nape to tail; whilst the back approaches the cross-bar stage, the white stripe on the hinder surface of the thigh is dissolved into irregular white spots. C. sccdaris is known only from near Chihuahua town, and plateau to the south of it, except two specimens "from Arizona" according to Cope. According to the evolution of the pattern from youth to adult age (for instance, the very pronounced white spots in the stripes), this lizard is closely allied to C. communis. CNEMIDOPHORUS COMMUNIS Cope. Diagnosis.-4 supraoculars. Collar strong, composed of at least |