1915.] 



THOMOMYS PEKPALLIDUS GEOUP. 



77 



Slcull. — Long, narrow, and slender, with nearly parallel lateral 

 ridges; zygomata parallel or slightly wider anteriorly; nasals long 

 and narrow; interparietal rectangular or oval, wider than long in 

 immature skulls; pterygoids long, low, and thin, with rounded 

 symphysis. 



Measurements. — Average of 7 male topotypes: Total length, 221; 

 tail vertebrae, 79; hind foot, 30. Average of 3 female topotypes: 

 208, 71, 28.7. SlcuU (of type): Basal length, 35; nasals, 14.5; zygo- 

 matic breadth, 23; mastoid breadth, 18; alveolar length of upper 

 molar series, 7. 



Remarks. — Thomomys cabezonx seems to be a local form not closely 

 connected with surrounding species. From peri)allidus, its nearest 

 neighbor on the east, and pallescens on the west, it is sharply differen- 

 tiated. In general appearance it most nearly resembles perpes, from 

 which it differs strikingly in large ears and in many cranial characters. 

 Two specimens from Whitewater show an overlapping of range 

 with perpallidus, but Gaut reports cahezonse in irrigated fields, and 

 perpallidus in the sagebrush. A single specimen of nigrescens from 

 2,500 feet altitude near Banning, and 7 specimens of cahezonse, show 

 a meeting or overlapping of ranges along the edge of the valley. 

 The narrow braincase suggests relationship with jacinteus, and with 

 neglectus of which it may be a pale valley form. 



Specimens examined. — Total number, 55, as follows: 

 California (southern): Banning, 12; Cabezon, 27; Schains Ranch (4,500 feet 

 altitude), 4; Snow Creek (near \ATiitewater), 2; Whitewater, 10. 



THOMOMYS OPERARIUS Merriam. 

 Owens Lake Pocket Gopher. 



(PI. V, fig. 4.) 



Thomomys operarius Merriam, Proc. Biol. Soc. Washington, XI, 215, July 15, 1897. 



Type. — Collected at Keeler, California, on east side of Owens Lake, 

 at 3,600 feet altitude, by E. W. Nelson, November 29, 1890. Type 

 specimen in U. S. Nat. Mus., Biological Survey collection. 



Distribution. — Known only from type locality (fig. 6). 



Characters. — Size medium, hind foot 30 mm.; color rich buff; 

 skull short and wide; mammae in 4 pairs. 



Color. — ^Upperparts rich buff or pale ochraceous; ear patch gTay 

 or plumbeous; underparts, feet, and tail creamy white. Young, 

 more gTayish. 



Skull. — Short and wide with short, heavy rostrum; zygomata 

 abruptly spreading; upper incisors sharply decurved or sUghtly 

 incurved; maxillaries short and heavy. 



Measurements. — Average of 5 topotypes ( c? ad.) : Total length, 

 223; tail vertebrae, 69; hind foot, 30.6. Average of 5 females: 217, 

 66, 29.6. Skull (of type): Basal length, 38; nasals, 13.5; zygomatic 



