24 Nelson and Goldman — New Mammals from Lower California. 



of skull; braincase much narrower and less inflated than in obscurns ; 

 huUiii smaller. 



Measurements of type. — Total length, 2;'.7; tail vertebrae, 117; hind foot, 

 33. Skull: basilar length, 27; zygomatic breadth, 18.3; interorbital 

 breadth, 8.5. 



Ammospermophilus leucurus insularis subsp. nov. 



ESPIRITU SANTO SPEKMOPHILE. 



Type from Espiritu Santo Island, Lower California, Mexico. No. 

 146,783, U. S. National Museum, Biological Survey Collection. 9 adult. 

 Collected February 7, 1906, l)y E. W. Nelson and E. A. Goldman. Origi- 

 nal number 10,072. 



General characters. — Similar to leucurus but larger, and underside of 

 tail grizzled witli black. 



Color (fresh winter pelage). — Top of head, back, and upper part of 

 sides grizzled brownish fawn color with a white stripe along eacli side of 

 back as in leucurus ; back of neck and middle <if sliouldcrs paler and more 

 grayish than rest of upperparts; shoulders and outside of hind legs dull 

 fawn color mucli less suffused with vinaceous than in peninsuliv ; under- 

 parts including lower cheeks, sides of neck and flanks, dull whitish; 

 npperside of tail blackish thinly mixed with dull white; underside dull 

 whitish usually more or less strongly grizzled witli l)lack and witli a ])lack 

 border. 



Skull. — Larger than that of leticurus or peninsulx ; rostrum broader 

 and heavier, and frontal area, including base of rostrum, fuller and more 

 arched ; bnlke proportionately smaller. 



Measurements of type. — Total length, 232; tail vertebra^, 77; hind foot, 

 36. Skull: basilar length, 32.6; zygomatic breadth, 24.6; interorbital 

 breadth, 10.5. 



Thomomys magdalenae sp. nov. 



MAGDALENA ISLAND POCKET GOPHER. 



Type from Magdalena Island, Lower California, IVIexico. No. 14(i,S32, 

 U. S. National Museum, Biological Survey Collection, c? adult. Col- 

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

 number 18,743. 



General characters. — Most closely related to T. h. anit;v of adjacent 

 mainland but much paler, more bufly; skull larger, more massive and 

 much more angular. Closely resembling russeolus in color, but skull very 

 different. 



Color (rather worn pelage). — Upperparts pale, slightly ochraceons, 

 bufly; underparts, including lips, dull creamy white; feet and tail tliinly 

 covered with wliitish Iiairs. 



Skull. — Similar in size to that of tyjncal bottie but nuich more massive; 

 rostrum shorter and heavier; ascending branches of premaxilhe broader; 

 zygomatic arclies much narrower posteriorly (not strongly bowed outward 

 as in bottx), sides less nearly parallel ; interorbital region broader; brain- 

 case more elongated, narrower, more squarely truncated posteriorly, 

 lambdoid crest less sinuous; bulhc larger. Compared with that of anitx, 



