122 Proceedings of the Biological Society of Washington. 



hairs of tail whitish. The dark plumbeous hair bases show through to 

 some extent on the underparts, and cause an appreciable darkening effect. 

 The same is true to a lesser extent above. Young specimens are in better 

 pelage than adults; the color of their upperparts is like that of adults, but 

 the underparts are more whitish. Every adult shows from one to four 

 molt lines, and in some specimens the pelage is obviously much worn. 



Skull. — Similar to that of Thomomys douglasii douglasii, but with shorter 

 brain-case, zygomatic width tending to be less and zygomata more nearly 

 square, the arches distinctly broader posteriorly than in douglasii. Similar 

 to that of T. d. limosus, but zygomatic width less, the arches less expanded. 



Measurements. — Tijpe: Total length, 230 mm.; tail vertebrae, 70; hind 

 foot, 33. Skull: Basal length, 34.5; nasals, 14.9; zygomatic breadth, 21.5; 

 mastoid breadth, 19.2; interorbital breadth, 6.3; alveolar length of upper 

 molar series, 8.3. Average of five males: Total length, 227 (max. 232, min. 

 222) ; tail vertebrae, 72 (76-70) ; hind foot, 32.6 (34-31). Skull: Basal length, 

 34.1 (34.5-33.6); nasals, 14.5 (14.9-14.0); zygomatic breadth (four speci- 

 mens), 21.6 (21.9-21.2); mastoid breadth, 19.0 (19.4-18.8); interorbital 

 breadth, 6.6 (7.0-6.1); alveolar length of upper molar series, 8.4 (8.6-8.2). 

 Average of three females: Total length, 206 (max. 215, min. 195); tail 

 vertebrae, 64 (70-60); hind foot, 30 (30-30). Skull: Basal length, 31.5 

 (32.0-31.3); nasals, 13.6 (14.0-13.2); zygomatic breadth (one specimen), 

 20.5; mastoid breadth, 18.0 (18.5-17.7); interorbital breadth, 6.4 (6.5-6.3); 

 alveolar length of upper molar series, 8.0 (7.9-8.3). 



Remarks. — Contrary, perhaps, to expectations, the Rainier Pocket 

 Gopher finds its closest affinities with the douglasii group, heretofore known 

 only from the lowland country west of the Cascade Mountains in Washing- 

 ton and Oregon, the Olympic Mountains, and the Washington side of the 

 Columbia River east to White Salmon, Klickitat County. Externally 

 and cranially the Rainier Pocket Gopher is similar to Thomoinys douglasii 

 limosus; and intergradation with this form is shown by specimens from 

 Signal Peak, Yakima County, and Trout Lake, Klickitat County. The 

 relations of the new form to the pocket gophers found east of its range are 

 not so clear. Specimens from Conrad Meadows, McAllister Meadows, and 

 Bumping Lake, on the east slope of the Cascade Mountains in Yakima 

 County, seem to show intergradation with the fuscus group. 



The new form has quite certainly ingressed to Mount Rainier from the 

 Cascade Mountains to the east, and is found at present only on the east 

 side of the Mountain, from about Cowlitz Divide to Grand Park. 



Specimens examined. — Total number, 15, as follows: 



Mount Rainier, Pierce County, Washington: Owyhigh Lakes, 5,100 

 feet, 6; Glacier Basin, 5,935 feet, 6. 



Yakima County, Washington: Twin Sister Lakes, near Cowlitz Pass, 

 5,300 feet, 1; 2 miles southwest of Conrad Meadows, 4,200 feet, 1; head 

 of Hindoo Creek on Mount Aix, 6,500 feet, 1. 



