180 -NORTH AMERICAN FAUNA. [No. 7. 



it is useful to remember Mr. Jouy's observation that the two species 

 live apart in separate localities. 



Sceloporus magister, according to this, inhabits the desert region of 

 southern California, as verified by numerous examples brought home 

 by the Death Valley Expedition and enumerated hereafter. Material 

 from the same source shows that it penetrates into southern Nevada, 

 and easterly into southwestern Utah, while Dr. Merriam, during Ms 

 San Francisco Mountain Expedition in 1889, demonstrated its occur- 

 rence in the Grand Canon of the Colorado. The most northernlocality 

 from which the species has been brought, and which has never before 

 been recorded, I believe, is the Big Bend of the Truckee Biver in Ne- 

 vada, at 'Camp 12' of King's expedition, where numerous specimens 

 were collected by Mr. Bobert Bidgway. Eastward it has been found 

 in the deserts of southern Arizona as far as Eort Yerde and Tucson. 



Sceloporus clarkii, on the other hand, within the United States, seems 

 confined to southeastern Arizona, whence it is found southward into 

 Mexico for an unknown distance, probably confined to the western 

 slope of the Sierra Madre, for it is pretty certain that S. clarldi and all 

 its allied forms, or species, are confined to the western slope of the 

 continent. 



The map used for plotting the distribution of the two species was 

 the summer 'Kain- chart of the United States' by Charles A. Schott 

 (published by the Smithsonian Institution in 1868) and the coincidence 

 of the dividing line between the two species with the isohyetal line of 

 6 inches seems to be more than accidental. 



Farther south in Mexico we find the typical S. clarldi replaced by a 

 nearly related form, which, as it has received no name before, we may 

 call S. boulengeri; * Boulenger's S. spinosus being in part this form. 



Still farther south we have another modification of the same type in 

 Sceloporus acanthinus Boc, with its excessively long points to the dorsal 

 scales. The locality whence came the type is St. Augustine, on the 

 west slope of the volcano of Atitlan, Guatemala. 



Sceloporus magister has also representative forms toward the south. 

 A very distinct species, but apparently of rather restricted distribu- 



* Sceloporus boulengeri, sp. uov., Plate I, figs. 5a.-c. 



Diagnosis. — Similar to S. clarJcii but with, fewer femoral pores ; ear spines com- 

 paratively short and broad; interparietal very broad. 



Habitat. — Mexico, west coast from Mazatlan to Guaymas. 



Type. — U. S. Nat. Mns., No. 14079 ; Presidio, about 50 miles from Mazatlan, Sinaloa, 

 Mexico; A. Forrer, coll. 



In the width of the interparietal the present form agrees with S. zosteromus, but 

 the latter has nearly twice as many femoral pores, and its ear spines are long, nar- 

 row, and numerous. 



