Mammals 51 



has the ears large, but hardly equal to their distance from tip of 

 nose; the tail very long, more than half total length, distinctly 

 pencilled. This includes P. crinitus auripectus of Allen, easily 

 recognized by the yellow spot on breast, and P. boylii rowleyi of 

 Allen, with no breast spot. The third group has short and round- 

 ed ears, and shorter tail, which is not pencilled. This series is 

 divided into the larger (about seven inches long) P. leucopus 

 tornillo of Mearns, and the smaller P. maniculatus, which has 

 races rufinus of Merriam, nebrascensis of Coues, and osgoodi of 

 Mearns. The nebrascensis and lutcus of Warren's Mammals of 

 Colorado are really osgoodi and nebrascensis respectively. 



The identification of our deer mice is not so difficult if the 

 localities are taken into account. Thus a very large-eared mouse 

 from the eastern foothills, Boulder, Colorado Springs, or Trinidad, 

 will be nasutus;* but in the western part of the State it will be 

 truei. An ordinary small-eared mouse will almost certainly be 

 one of the maniculatus forms. Of these, rufinus, according to 

 Warren, is found from the eastern foothills of the Continental 

 Divide, and from west of the Pike's Peak range to the Utah line, 

 and from the north to the south boundary of the State, except 

 that in most of Routt and Rio Blanco, and western Garfield and 

 Mesa Counties it is replaced by the paler, less fulvous osgoodi. 

 The range of the latter is practically all of the State not occupied 

 by rufinus. The true nebrascensis form has taken at Fort Collins, 

 in the osgoodi territory. It is a light tawny mouse. 



The Arvicolidae include Ondatra, the musk rat; Phenacomys, 

 the mountain voles; Evotomys, the red-backed voles; and Micro- 

 tus, the voles proper. The musk rat, known by its large size and 

 aquatic habits, needs no description. Hollister** recognized two 

 races in Colorado. 0. zibethicus osoyoosensis of Lord, found in 

 the mountains, is large and dark; 0. z. cinnamominus of Hollister, 

 belonging to the plains region and foothills, is smaller and pale 

 reddish or brown. But in Boulder County cinnamominus goes 

 up to Ward, about 9,200 feet. The original osoyoosensis came 

 from Lake Osoyoos, British Columbia. Phenacomys is a rare 

 genus, distinguished by the character of its teeth. P. intermedius 

 of Merriam (determined by A. B. Howell) was taken by Warren 



*P. nasutus has also been taken by Warren in the San Luis Valley, near San Acacia. 

 **A Systematic Synopsis of the Muskrats. North American Fauna No. 32 (1911). 



