1906,] ON EVOLUTION IN MEXICAN LIZARDS. 277 



3. A Contribution to the Study of Evolution based upon the 

 Mexican Species of Cnem'idopliorus. By Hans Gadow, 

 F.RS., F.Z.S. 



[Received Marcli 2, 1906.] 

 (Plate XX. and Text-figures 61-83.) 



Contents. 

 Gesieeal Part. 



Conclusions arrived at from the study of the diflTerentiation, variability, and 

 distribution of these Lizards, pp. 277-299. 



Systematic Paet. 

 Key to the main groups of Mexican and North-American Cneniidophori, p. 300. 

 Description of the various kinds of Cnemidopliorus with special reference to their 



variations, p. 309. 

 Characters of South-American Cnemidophori, p. 301. 



C communis occidentalis, p. 339. 



C, communis copei, p. 346. 



C commwiis australis, p. 352. 



C. sexlineatus, p. 302. 

 C. hyperythr%is, p. 307. 

 Deppei-Geoup, p. 308. 



C. deppei, p. 309, C. deppei, var. 



coztunela, p. 316. 

 C. guttalus guttatus and C. g. 

 imm.utaMlis, p. 320 

 Gulaeis-Geoup, p. 327. 



Tabulation of characters of the 



^«7«)';s-Group, p. 329. 

 Key to the species &c., p. 328. 

 C. mariarum, 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 hocourti, p. 356. 

 C TOe.fi(?«w!ts, p.358. Tabulation 



of characters, p. 362. 

 C. mexicanus, var. balsas, p. 363. 

 Tessellatos-Geoup, p. 367. 

 Key to the species &c., p. 368. 

 C. p)erplexus, p. 368. 

 C. tessellatus, p. 369. 

 C. maximus, p. 371. 

 C. ruhidus, p. 371. 

 C. melanostethus, p. 372. 

 C martf/ris, p. 373. 

 C. octolineahis, p. 373. 

 C. inornatus, p. 373. 

 C. labialis, p. 374. 



References to the original descriptions of species, pp. 374-375. 

 Map: Plate XX. 



It was in the forest and bush region of the Atlantic Tierra 

 caliente, on the confines of the States of Oaxaca and Yera Cruz, 

 that I first beca,me 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 

 Ci'uz, was C. depp>ei and the large, conspicuously striped C. im- 

 muiahilis. These kept on further inland until near the foot of 

 the abrupt southern edge of the plateau. The small C. dep)pei 

 ceased, and a very large, tiger-barred lizard, G. mexicanus, made 

 its appearance. The striped C. immidahilis seemed to continue, 

 but on closer examination it was found that all the striped mid- 

 sized to large specimens were the young and immature of C. mexi- 

 canus, which reigned supreme on the open southern plateau until 



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