1915.] 



THOMOMYS BOTT^ GROUP. 



61 



Distribution, — ^Ejiown only from type locality (fig. 7). 



Characters. — Smaller than anitse or nigricans, with tiny ears, slender 

 skuU, thin hair, and pale buffy coloration. 



Color. — ^About as in perpallidus, or slightly brighter. October 

 specimens: Upperparts varying from pale to bright buffy; nose 

 grayish; small ear patch dusky; underparts pale buffy, becoming 

 whitish on throat; feet and tail thinly clothed with whitish hairs. 



Skull. — Light and slender, mth narrow braincase, short narrow 

 posteriorly truncate nasals, wide premaxiUse, slender pterygoids^ 

 full rounded bullje, and narrowly constricted shaft of basioccipital. 

 Dentition: Incisors abruptly decurved at right angles to axis of skuU. 



Measurements. — Type ( c? young ad.): Total length, 208; tail 

 vertebrae, 73; hind foot (dry), 30. Topotype young ad.): 225, 

 82, 27 (dry). Topotype ( 9 im.): 88, 60, 27 (dry). ^ ShuU (of type): 

 Basal length, 35.5; nasals, 12.7; zygomatic breadth, approximately 

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

 upper molar series, 7.5. 



Remarlcs. — While in color practically identical with magdalense and 

 very similar to perpallidus, this desert form differs in cranial charac- 

 ters from magdalense and anitse in fight slender skuU, slender ptery- 

 goids, large rounded bullae, and narrow basioccipital; and from 

 perpallidus in narrow braincase, wider premaxiUge, and uniformly 

 truncate nasals. The characters strongly suggest a little slender- 

 skulled form of perpallidus. The type specimens are from an oasis 

 in a sandy desert where they were apparently isolated, but speci- 

 mens from Rosarito on the north and San Jorge on the south appa- 

 rently intergrade with anitse. 



One specimen from San Jorge and two from Rosarito might be 

 thrown with russeolus (though the majority from the same places 

 are nearer anitse), and on this account this form was made a sub- 

 species of hottx rather than of perpallidus. 



Specimens examined. — Four, from type locafity. 



THOMOMYS MAGDALENE Nelson & Goldman. 

 Magdalena Pocket Gopher. 



(PL V, fig. 12.) 



Thomomys magdalenx Nelson & Goldman, Proc. Biol. Soc. Washington, XXII, 24, 

 Mar. 10, 1909. 



Type. — Collected at Magdalena Island, near west coast of Lower 

 Cafifornia, by E. W. Nelson and E. A. Goldman, December 3, 1905. 

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



Distribution. — ^Magdalena Island, Lower Cafifornia (fig. 7). 



CJiaracters. — Larger than anitse, with heavy, angular skull; color 

 paler; hair thin. 



