1914] Grinnell: Four New Pocket Gophers from California 315 



braincase, and less squarely spreading zygomatic arches. From topo- 

 types of T. a. pascalis Merriam, infrapallidus differs in paler colora- 

 tion ventrally. larger feet, higher brainease. more projecting incisors 

 and smaller auditory bullae. 



Thomomys nigricans puertae, new subspecies 

 La Puerta Gopher 



Type. — J 1 young adult, no. 7511, Mus. Vert. Zool. ; La Puerta 

 (Mason's Ranch), eastern San Diego County. California; May 31, 

 1909; collected by F. Stephens; original no. 1974. 



Diagnosis. — A pale desert-slope race of Thomomys nigricans 

 nigricans Rhoads ; apparently identical in size and cranial characters 

 with that race; pelage mid-dorsally and around ears with far less 

 admixture of black; general tone of coloration both above and below, 

 ochraceous-tawny (of Ridgway, 1912), brightest on sides, and slightly 

 subdued with dusky down middle of back; spot of sooty behind ear; 

 face dusky. 



Material. — The Museum contains forty-three specimens labelled La 

 Puerta (nos. 7510-7519, 7582-7586, 16636-16654, 18822-18830). 

 These are all of Mr. Stephens's collecting. According to his field 

 notebook, the majority were caught in cultivated land on Mason's 

 Ranch, which is located at the lower end of La Puerta Valley. Others, 

 however, were taken on surrounding hillsides. Mason's Ranch is five 

 miles west of Vallecito, on the old overland (Butterfield) stage-road. 

 La Puerta Valley is evidently arid Lower Sonoran. Along the course 

 of the stream arrowweed (Pluchca) is a common plant, while there 

 is an occasional mesquite. The valley floor is mostly covered with 

 large creosote bushes (Larrea). 



Comparisons. — The series of La Puerta gophers is notably variable 

 in color-tone. Picked specimens are fully as dark as the average of 

 topotypes of nigricans, from Witch Creek, on the west side of the 

 Cuyamaca .Mountains. La Puerta is well down on the desert or east 

 slope of the same general mountain mass, and less than ten miles 

 away, so that it is quite possible that a continual invasion of true 

 nigricans down on the east slope brings good examples of that form 

 into the same valley with the more remotely derived and hence differ- 

 entiated type here named puertae. Upon this theory the series at 

 hand may be divided into bright-colored and dark-colored sections, 

 the former meriting the name puertae, the latter nigricans. 



