22 BULIiETIN 99, UNITED STATES NATIONAL. MUSEUM. 



evident that new subspecies of Protoxerus should not be named 

 unless based on good series of specimens. The most common varia- 

 tion is in the intensity of the " reddish ' ' color on the back and espe- 

 cially on the rump and hind hmbs. In our series this varies from 

 Sudan brown to chestnut, or even, in one specimen, blackish. The 

 single blackish specimen has the upper sides of the hands and feet 

 largely pure glossy black. 



Genus XERUS Hemprich and Ehrenberg. 



1832. Xerus Hempkich and Ehrenberg, Symb. Phye., vol. 1, sig. e e (text to 



pi. 9). {X. brachyotus.) 

 1842. Spermosciurus Lesson, Nouv. Tabl. Anim., p. 110. {X. rutilus.) 

 1850. Xeros Burmeister, Verz. Mus. Halle-Wittemb., p. 15. (pro Xerus.) 



In addition to the two well-marked forms of this ground-squirrel 

 which are represented in our collection, several subspecies have 

 been named from northern British East Africa, Abyssinia, and 

 Somahland. 



For measurements of the specimens of this genus see page 23. 



XERUS RUTILUS RUFIFRONS Dollman. 



1911. Xerus dahagala rufifrons Dollman, Anu. and Mag. Nat. Hist., ser. 8, vol. 7, 

 p. 518. May. (Northern Guaso N>dro, British East Africa; type in 

 British Museum.) 



Specimens. — Thirteen, from the following localities: 



British East Africa: Archer's Post, Northern Guaso Nyiro, 1 

 (HeUer) ; Isiola River, 1 (Heller) : Kara Water, Marsabit Road, 3 

 (HeUer); Kenya Water, Marsabit Road, 1 (HeUer); Merelle Water, 

 Marsabit Road, 4 (HeUer); Mount Nyiro, south of, 1 (Percival); 

 Northern Guaso Nyiro River, 1 skull (K. Roosevelt); Quoy Water, 

 Marsabit Road, 1 (Heller). 



There is considerable variation among the skins of this series in the 

 extent of the red on the cro^vn and also in the amount of black on the 

 head and nape. The general color of the back varies greatly in the 

 amoimt of blackish speckling, extent of the yeUowish-buff dorsal 

 area, and in the intensity of the vinaceous ground color. The skins 

 from more northern localities are paler than those from Archer's Post 

 and Isiola River and are doubtless approaching some one of the 

 Abyssinian foi-ms in color. 



A female collected at Archer's Post, September 23, contained two 

 large embryos. 



XERUS RUTILUS SATURATUS Neumann. 



1892. Xerus rutilus True, Proc. U. S. 'Nat. Mus., vol. 15, p. 467. (Specimen 



from Taveta; not of Cretzschmar.) 

 1900. Xerus saturatus Neumann, Zool. Jahrb., Syst., vol. 13, p. 546. (Kibwezl, 



British East Africa.) 



Specimens. — Two, as follows: 



British East Africa: Taveta, 1 (Abbott); Voi River, Taita Hills, 

 1 (Heller). 



