1915.] 



THOMOMYS FULVUS GROUP. 



81 



Mexico to Sierra Grande, and the White and Guadalupe Mountains; 

 north to Fisher Peak, southeastern Colorado (fig. 7). 



Cliaracters. — Size medium; hind foot 28-30 mm.; color dark 

 tawny or dull chestnut; ears and claws medium; mammae in 4 pairs, 

 ingumal 2-2, pectoral 2-2. 



Color. — Summer pelage: Upperparts clear dark tawny or light 

 chestnut, often dusky or blackish along back; ear patch, nose, and 

 cheeks dusky or blackish; underparts lighter; chin, lining of cheek 

 pouches, and feet usually wliite or whitish; tail tawny or dusky 

 above, grayish below. Winter pelage: Duller darker tawny, more 

 uniformly dusky above. Young very similar to adults. 



SJcull. — Heavier and relatively wider than in the fuscus or fossor 

 groups; Hghter and slenderer than in perpallidus or aureus. Lateral 

 ridges slightly developed and approximately parallel at all ages; 

 nasals broadly emarginate posteriorly; bullae medium; basioccipital 

 broadly triangular; pterygoid fossa normally V-shaped. Dentition: 

 Incisors not projecting beyond tip of nasals; distinctly grooved. 



Measurements. — Old male topotype: Total length, 231; tail verte- 

 brae, 74; hind foot, 30. Average of 5 male topotypes: 219, 70, 

 30. Average of 5 female topotypes: 209, 66, 29.2. SJcull (of topo- 

 type, d ad.):^ Basal length, 36; nasals, 15; zygomatic breadth, 24; 

 mastoid breadth, 19; interorbital breadth, 6; alveolar length of upper 

 molar series, 8. 



Remarlcs. — The typical subspecies of Tliomomys fulvus seems to 

 occur only in the Transition Zone, above which it rarely extends and 

 below which it extends mainly in modified forms, several of which 

 have been separated. The name fulvus stands not only for a species 

 with its six subspecies, but for the center of a widely distributed 

 group, including mearnsi, haileyi, and lachuguilla. Its relationship 

 with the hottx group of the west coast is genetically close but 

 geographically the two are widely separated. If connected with the 

 perpallidus group it is through toltecus and cervinus, but this con- 

 nection seems doubtful and by no means close. 



Specimens examined. — Total number, 305, as foUows: 



Arizona: Aubrey (10 miles south of Pine Spring, 6,000 feet altitude), 2; Beaver 

 Creek (near Fort Verde), 1; Bill Williams Mountain, 2; Blue (Greenlee 

 County, 6,000 feet), 2; Bradshaw City, 17; Flagstaff, 2; Fort Verde, 5; Fort 

 WMpple, 2; Fossil Creek, 3; Grand Canyon (Canyon Spring), 1; Little Spring 

 (18 miles northwest of Flagstaff), 1; Pine Spring (5 miles north, 7,000 feet), 

 1; Prescott, 7; Prieto Plateau (south end Blue Range, Greenlee County, 

 7,500-9,000 feet), 6; San Francisco Mountain, 20; Springerville (7,000 feet), 

 29; Trumbull Mountains, 3; White Mountains, 3. 



Colorado: Fisher Peak, 1. 



98121°— 15 



iNo. 24506, U. S. Nat. Mus. 



