The vegetation at the above-named localities is a combination of brush and grasses that are both more luxuriant than in areas dominated by pinyon and juniper on the more southern and altitudinally lower part of the top of the Mesa where no _M. longicaudus_ was taken. Microtus mexicanus mogollonensis (Mearns) Mexican Vole _Specimens examined._--Total, 22: Prater Canyon, 7600 ft., 76283-76287; Sect. 27, head of east fork of Navajo Canyon, 7900 ft., 69442; Far View Ruins, 7700 ft., 69443, 79223-79224; 2 mi. NNW Rock Springs, 7900 ft., 69444-69446; Park Well, 7450 ft., 69447-69453; rock ledge at head of Spruce Tree Canyon, unnumbered specimen in Denver Museum; Headquarters, MV 7895/507, 7896/507. The first specimen of the Mexican vole from Colorado was obtained on the Mesa Verde and has been reported by Rodeck and Anderson (1956:436). Specimens have now been taken at seven localities on the Mesa. Prater Canyon is the only one of these localities at which any other species of vole was taken. There _Microtus longicaudus_ and _Microtus montanus_ were also obtained. Judging from the vegetation at the above localities, _M. mexicanus_ is to be expected in drier areas with less cover than _M. montanus_ inhabits, and in areas having less cover than those inhabited by _M. longicaudus_. Microtus montanus fusus Hall Montane Vole _Specimens examined._--Total, 16: Upper Well, 7575 ft., 69454-69465; 1/4 mi. N Middle Well, 7500 ft., 69466-69469. The voles were trapped in the dry but dense meadow of grass and sedge covering the floor of the canyon (see Plate 1). _Sorex vagrans_ was trapped in the same places. Four of the females of _M. montanus_ trapped on September 3, 1956, were pregnant. Erethizon dorsatum couesi Mearns Porcupine _Specimens examined._--Total, 2: 69470, old [Female], and 69471, her young male offspring, both obtained on August 28, 1956, in the canyon of the Mancos River, 6200 feet, along the western side of the River. I saw no other porcupine in the Park.