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Show 1906.] ON EVOLUTION IN MEXICAN LIZARDS. 277 3. A Contribution to the Study of Evolution based upon the Mexican Species of Cnemidophorus. By HANS GADOW, F.R.S., F.Z.S. [Received March 2, 1906.] (Plate XX. and Text-figures 61-83.) CONTENTS. GENERAL PART. Conclusions arrived at from the study of the differentiation, variability, and distribution of these Lizards, pp. 277-299. SYSTEMATIC PART. Kejr to the main groups of Mexican and North-American Cnemidophori, p. 300. Description of the various kinds of Cnemidophorus with special reference to their variations, p. 300. Characters of South-American Cnemidophori, p. 301. C. sexlineatus, p. 302. C. hyperythrus, p. 307. DEPPEI-GROUP, p. 308. C. deppei, p. 309, C. deppei, vai cozumela, p. 316 C. guttatus guttatus and C. g. immutabilis, p. 320. GULARIS-GROUP, p. 327. Tabulation of characters of the gularis-Group, p. 329. Key to the species &c, p. 328. C. ma riarum, p. 328. C. gularis, p. 330. C. semifasciatus, p. 334. C. septemvittatus, p. 335. C. scalaris, p. 335. C. communis, p. 337. Tabulation of characters, pp. 340, 348. C. communis occidentalis, p. 339. C, communis copei, p. 346. C. communis australis, p. 352. C. communis bocourti, p. 356. C. mexicanus, p. 358. Tabulation of characters, p. 362. C. mexicanus, var. balsas, p. 363. TESSELLATUS-GROUP, p. 367. Key to the species &c, p. 368. C. per plexus, p. 368. C. tessellatus, p. 369. C. maximus, p. 371. C. rubidus, p. 371. C. melanostethus, p. 372. C. martyris, p. 373. C. octolineatus, p. 373. C. inornatus, p. 373. References to the original descriptions of species, Cpp.. l37a4b-i3a7l5.i s, p. 374. Map: Plate XX. It was in the forest and bush region of the Atlantic Tierra calieute, on the confines of the States of Oaxaca and Vera Cruz, that I first became personally acquainted with Cnemidophorus. There was only the spotted, large C. guttatus, but further east, where the Savannah begins, its place was taken by the small, striped C. deppei. On the Pacific side of the Isthmus, at Tehuantepec and Salina Cruz, was C. deppei and the large, conspicuously striped C. immutabilis. These kept on further inland until near the foot of the abrupt southern edge of the plateau. The small C. deppei ceased, and a very Large, tiger-barred lizard, C. mexicanus, made its appearance. The striped C. immutabilis seemed to continue, but on closer examination it was found that all the striped midsized to large specimens were the young and immature of C. mexicanus, which reigned supreme on the open southern plateau until 19* |