346 DE. H. GADOW ON EVOLUTION [Mar. 20, 



munis and lead on to the Puebla clan, in vvliich the characters of 

 C communis aie again intensified. 



There is still a gap between Sau Juan del liio and Puebla, 

 a distance of 15U miles, whence no C'tie^nidojihori have been 

 recorded. I myself have never seen a single specimen in the 

 Valley of Mexico, an absence due no doubt to the high eleva- 

 tion, the limit for this genus being apparently near 7100 feet. 

 Dr. Meek found them in abundance near Puel^la, 7100 feet, 

 but the Capital, itself in the depression of the so-called valley, lies 

 some 300 feet higher. San Juan's elevation is 6000 feet, and 

 any way thence to Puebla would imply an ascent of more than 

 8000 feet, an elevation which may well be piohibitive to any 

 species of Cnemido^ihortcs. At Amecameca, which lies at this 

 altitude, I looked for them in vain. It is therefore more likely 

 that the Puebla clan have ariived there by some roundabout 

 way at present unknown. But it is ceitain that there is no 

 communication between them and those of Yautepec and Cuantla 

 in Morelos, although the distance would be less than 40 miles. 



Consequently it seems rather likely that the spotted clan at 

 Pue1)la, with its isolation from the other C communis^ represents 

 a case of convei-gent evolution. C. c. balsas itself is a case of 

 isolation ; they ai'e restricted to the basin of the Balsas, bounded 

 on the north by the impassable l)ai'rier of high mountains, the 

 southern fringe of the Central plateau, and on the south by the 

 Siena Madre del Sur, the low pass of which, at Los Cajones, 

 these lizards just manage to ci'oss, but they do not descend 

 beyond, into the Coastal region. What hapjiens to these Cnevii- 

 dojyJiori in Western Michoacan, whether they change or not, 

 into the western form, remains for the present unknown. The 

 same applies to the zoologically undiscovered wide districts of 

 the upper basin of the Balsas. 



ONEMiDoriioRus COMMUNIS coPEi. (Text-figs. 78 A, C, E.) 



Diflering from G. communis occ-idenialis by the increased number 

 of humeral and femoral rows, greater number of pores, and laiger 

 size of the l)ody. 



Although these are diflei'ences of degi'ee only, they are signi- 

 ficant because they lead to and are combined with furtliei- modi- 

 fications which change such lizai'ds in Oaxaca and on the Isthmus 

 into a form to which the name of conmiunis is no longer 

 applicable. 



Of the specimens described in the accompanying table (p. 348), 

 only those from Colima, Manzanillo, San Domingo de Guzman, 

 and apparently those fiom the island of Oozumel, confoini with 

 C. communis co^jei. Possibly those mentioned l)y Cope from 

 Guatemala may exhibit the same chai-acteis, especially the 

 forearm scutes. 



Cope's types, about 40 specimens, were sent to Washington by 

 Xantus, AvJio had collected them in the State of Colima, Western 

 Mexico. In the original description. Trans. Am. Phil. Soc. 1877, 

 p. 95, it is stated that C. communis has a frenocular, lai'ge post- 



