THpodomys phillipsi Gray. 85 



northeastern point of the Valley of Mexico, at the base of the Sierra de 

 Pachuca, the latter forming the limit of the valley in this direction. At 

 an altitude of about 9,000 feet, and about three or four miles in a direct 

 line higher up in these mountains, lies the mining town of Real del 

 Monte, the reputed type locality. The mountains are almost wholly 

 composed of porphyry, with only a very scanty coating in places of a 

 hard, clavey soil. A short visit to this locality was enough to show very 

 conclusively that no species of this group had ever been taken in its im- 

 mediate vicinity. A visit to the northern slope of the mountains near 

 El Chico showed it to possess the same character. 



" The next effort was made in the forlorn hope of finding the species 

 about the border of the valley, at the base of the mountains, near 

 Pachuca. A careful search of this vicinity for some miles in various 

 directions failed to discover any sign of kangaroo rats or, indeed, any 

 sufficient area of suitable ground. A trip w T as then made to the village 

 of San Augustin, 18 miles south of Pachuca, in the Valley of Mexico, and 

 this also resulted in finding the same rocky hills and hard clayey bot- 

 toms that prevail about the northern end of the valley. 



" Giving up all hope of finding the species near Pachuca or Real del 

 Monte the alleged type locality I decided to make another search for 

 it at Irolo, which lies a little more than 25 miles south of Pachuca, in 

 Hidalgo, and just east of the low divide which borders the Valley of 

 Mexico on the east between the Sierra de Pachuca and the northern end 

 of the Sierra Nevada de Iztaccihuatl. The course of the Vera Cruz or 

 Mexican railway, on which I traveled, at first kept to the south near the 

 west side of the divide. Some six miles out of Pachuca we passed over 

 a narrow belt of softer soil than usual here, and I had hasty glimpses of 

 several burrows among the maguey plants that I was quite certain be- 

 longed to some species of kangaroo rat. The road then left the divide 

 and sw r ung out into the Valley of Mexico, and the soil again became a 

 hard clay. From the station of Ometusco, just within the Valley of 

 Mexico, the road leads east for a few miles over a low dividing ridge to 

 Irolo. About the latter place and away to the northward, toward the 

 mountains of Pachuca, the bases of the low hills and ridges show pale 

 yellow shades such as sandy deposits would give. A short search about 

 the base of the hills near Irolo showed that areas of sandy and loose soil 

 did in feet exist there. 



" Further search showed that these areas of soft soil were occupied by 

 kangaroo rats, which when captured, however, proved to be a 5-toed 

 J'i'i'otli/nts instead of a 4-toed Dipodomys. No trace of any other species 

 could be found, but the Perodipus was abundant. 



'' From the fact that the belt of country in which this species occurs at 

 Irolo extends directly toward the point where I saw the signs on the 

 road from Pachuca, with less than twenty miles intervening and a divide 

 of not over 250 feet. I feel fully justified in assuming that the animals 

 whose burrows were seen near Pachuca are a colony of the same species 

 as that found at Irolo, namely, a Pcrodipus. 



