70 



NOETH AMEKICAN FAUNA. 



[no. 39. 



THOMOMYS PERPALLIDUS ALBATUS Grinnell. 

 White Pocket Gopher. 

 (Pl..V,fig. 1.) 



Thomomys albatus Grinnell, Univ. of Cal., Publ. Zool., X, 172, 1912. 



Type, — Collected on west side of Colorado River at old Hanlon 

 Rancli near Pilot Knob, Imperial County, California, by J. Dixon, May 

 7, 1910. Type specimen in Mus. Vert. Zool., Univ. of California. 



Distribution. — Southeastern California and northeastern Lower 

 California fiom Carrizo Creek south to Gardner's Lagoon, Salton 

 River (fig. 6). 



Characters. — Size considerably larger than perpallidus; color 

 lighter; ears small; tail long; feet stout; mammse in 4 pairs. 



Color. — Summer pelage (May and June) : Upperparts pale buff or 

 cream color; nose and ears grayish brown; underparts white or 

 creamy with Uttle or no plumbeous base to fur; feet and tail almost 

 naked but with scattered short white hairs. Winter pelage: Prac- 

 tically as in summer, but mth more evident plumbeous base to fur on 

 belly. Young: Less buffy, more grayish white. 



SlcuU. — In old males rather heavy, ridged, and angular, widest at 

 anterior angle of zygomata; rostrum short and heavy; incisors not 

 so abruptly decurved as in perpallidus; bullae full and rounded; 

 occiput rather sloping, not so abruptly truncate as in aureus and 

 perpes. 



Measurements. — Type ( c? ad.) : Total length, 272 ; tail vertebrae, 100; 

 hind foot, 35. Topotype ( ad.): 264, 91, 34. Topotype (9 ad.): 

 229, 79, 34. Sltull (of type) : Basal length, 41.5; nasals, 15; zygomatic 

 breadth, 28; mastoid breadth, 22; interorbital breadth, 6.8, alveolar 

 length of upper molar series, 8.5. Skull of old female: 38, 13.5, 25, 

 21, 6.5, 7.7. 



Remarks. — This is a robust gopher very close to perpallidus in 

 color, but in size and skull characters close to aureus. It occupies 

 the moist, white, river sand of the flats where there is an abundant 

 food supply. Specimens from Carrizo Creek are not typical but 

 nearer albatus than perpallidus. Others from Baregas Spring and 

 west of the Salton Sea are nearer perpallidus. 



Specimens examined. — Total number, 72, as foUows: 

 California: Carrizo Creek^ 18; Colorado River bottoms opposite Yuma, 37; Salt 



Creek (Imperial County), 11; Salton Sea (Imperial County), 6. 

 Lower California: Salton River (Gardners Lagoon), 1. 



