1915.] 



TIIOMOMYS FOSSOE GEOUP. 



Ill 



Th.omom.ys fossor Group. 

 THOMOMYS FOSSOR Allen. 



Colorado Pocket Gopher. 

 (PI. II, fig. S; PI. VII, fig. 13; text fig. 4.) 

 Thmnomys fossor Allen, Bui. Am. Mus. Nat. Hist. V, 51, April 28, 1893. 



Type. — Collected at Florida, La Plata County, Colorado, altitude 

 7,200 feet, by Charles P. Rowley, June 25, 1892. T3rpe specimen in 

 Am. Mus. Nat. Hist. 



Distribution. — Mountains of western Colorado, extreme southern 

 Wyoming, northern New Mexico, eastern and southern Utah, and 

 northwestern Arizona (fig. 8). 



Characters. — Size medium, hind foot averaging about 29 mm.; 

 color dull and dark brown; ears large; skull long, low, and narrow, 

 with rostrum especially slender in profile, as in the talpoides group; 

 mammae in 5 pairs, inguinal 2-2, pectoral 3-3. 



Color. — Summer pelage: Upperparts dull dark brown with some- 

 times a rich chestnut tone; ear and postauricular patch black; nose 

 and face dusky; underparts buffy or ochraceous; part of feet and tip 

 of tail usually whitish; chin usually, and spot on breast sometimes, 

 white. Winter pelage: Duller, more grayish or drab. Young: In 

 summer paler and more buffy than adults. 



SlcuU. — Long and slender, with long rostrum, and anteriorally con- 

 verging temporal ridges; nasals nan'ow, with generally rounded pos- 

 terior tips; interparietal triangular; bullge large and full, basi- 

 occipital narrowed between them. Dentition very light. 



Measurements. — Average of 4 female topotypes: Total length, 221; 

 tail vertebrae, 63; hind foot, 29. A large male measures 220, 68, 32. 

 Slcull (of type, j ad.) : Basal length, 37; nasals, 15; zygomatic breadth, 

 22; mastoid breadth, 20; alveolar length of upper molar series, 7.5. 

 Skull of adult male from Lake City, Colo.ii 34, 13.5, 21, 18.7, 7. 



RemarJcs. — This is a wide-ranging boreal species with long, soft fur, 

 which even in midsummer does not become so short and harsh as in 

 low-country species. At high altitudes the long coat seems not to be 

 entirely lost during the brief summer. 



As might be expected there is some slight variation in specimens 

 from different mountahi ranges, some of which are entirely isolated by 

 low country, but nowhere is there enough variation to warrant 

 further subdivision. In such a variable group it is a great satisfac- 

 tion to find an occasional species that holds its distinctive characters 

 over a wide area. 



Specimens examined. — ^Totai number, 183, as follows: 



Arizona: Bright Angel Spring (Kaibab Plateau), 3; DeMotte Park (Kaibab 

 Plateau), 3. 



iNo. 48190, U. S. Xat. Mus. 



