1905.] AMPHIBIANS AND REPTILES. 213 



Cienosaura, and we will not discuss the question which of the two 

 groups is the more primitive ; apparently the latter, but this can 

 be contested. 



Grotaphytus, a typical old Northern Sonoran genus with several 

 species in Western United States. C. loislizeni ranging from 

 Oregon and Nevada into Sonora and Chihuahua ; C. collaris also 

 into Nuevo Leon. 



Holbrookia, from Texas and California into the dry parts of 

 Northern Mexico. H. maculata into North Sonora, H. texana to 

 Monterey and Lerdo near Torreon. I found it I'unning about 

 swiftly on the almost barren shaly ground near El Paso. H.pro- 

 pinqtm from Texas to Presidio near Mazatlan. 



Uta, with most species in South-western United States and in 

 Lower California. U. elegans from Utah to Texas and Sonora ; 

 U. stansburiana from Utah to Torreon. U. lateralis from Presidio 

 and Tres Marias Islands and U. bicarinata are Mexican, from 

 Pi"esidio to Tehuantepec, and everywhere between these places. 

 Otherwise strictly confined to the western side of the plateau and 

 the coast, it has entered the plateau at Cuernavaca and Puebla. 

 I have almost invariably found it on the stems and bi'anches of 

 low trees, upon which they flatten themselves like arboreal 

 Sceloporus ; rather remarkable, since the other species are so 

 decidedly dwellers on the sandy or stony ground. Very important 

 is the occurrence of a species, U. auricidata, on the Revilla 

 Gigedo Islands, 280 miles south of Cape Lucas, Lower Cali- 

 fornia, and nearly 350 miles from the coast of Jalisco. This 

 genus is typically Sonoi'an, witli its centre around the Gulf of 

 California. 



Phrynosoma, " Animal rey," or " Camaleon," or " Escorpion." 

 The original centre of this genus is undoubtedly Sonoraland, 

 whence it extends now over most of the Central, South-western, 

 and "Western States of North America and over the whole of 

 Mexico as far as Guatemala. Ph. cornutum, modestum, and 

 orbictdare are, in Mexico, scattered over the plateau. Ph. asio 

 is the most southern and at the same time the largest and most 

 handsome species, ranging from Colima to Guatemala. Stejneger 

 and Cope have already remarked on the "metachrosis" of 

 Ph. douglasi. I have found Ph. modestimn near El Paso of 

 exactly the same delicate French-grey colour as the little slabs 

 of Cretaceous limestone with which the hills are strewn ; the 

 same species at San Marcial and at Rincon in Mexico, on the red 

 and sandy volcanic rubble of that hilly desert region, were of the 

 same pronounced red tint. Examination with a magnifying- 

 giass showed the spirit-specimens to be covered with the iron- 

 stained red sand, but those which I have brought home alive 

 show this same red colour also to be that of their genuine skin. 



Sceloporus may well be called the most characteristic genus of 

 Mexican Lizards. Of the 34 species recognised by Boulenger, 

 28 occur in Mexico, between El Paso and Tehuantepec. Only 

 4 live in the United States, and only 3 or 4 are found south of 



