Mr. O. Thomas on new Ground-Squirreh. 387 



broad, considerably more than half the whole length of 

 tegmina, which has brought about the shortening of the tlnee 

 p per ulnar areas. 



Genus Heteropsaltria. 

 IIete)'opsaltria, Jacobi, SB. Ges. natui-f. Fr. Berl. 1902, p. 73. 

 Type, //. oliena, Jacobi. 



L. — New Ground-Squirreh of the Xerus erythropus Group. 

 By Oldfield Thomas. 



In working out some ground-squirrels from Luke Chad 

 presented by Capt. Gr. B. Gosling to the British Museum 

 I have examined all the specimens assigned to Xerus 

 erythropus, and find that, although very similar throughout 

 the vast range of the group, they can be divided into two 

 species by the size of their premolars, the East-African 

 animal having these teeth noticeably smaller than in the other 

 cases. 



Of each of these two species again there is evidence of 

 several geographical subspecies, so that six forms are distin- 

 guishable, as in the following synopsis : — 



A. Posterior upper premolar large, subquadran- 



gular. 



a. Back uear clay-colour ; forearms bufi. 



a'. West Africa X. eri/t/irojjus, Geoff. 



b'-. Abyssinia and Egyptian Soudan X. e. leucoumbrinus, 



b. Colour lighter; back near "pinkish buff"; [Riipp. 



forearms " cream-buff." Lake Chad .... X, e. chadeyisis, 



c. Back blackened, approaching " mummy- [subsp. n. 



brown " ; forearms •' cinnamon." Unjoro. X. e. lacustn's, 



B. Posterior upper premolar small, cylindrical. [subsp. n. 



a. Back dull clay-colour; I'orearuis dull buff'y . X. Dticrodon, sp. n. 



b. Back tawuy ochraceous; forearms between [subsp. n. 



" ochraceous " and " clay-colour " X. m.fulvior, 



All the current synonyms of X. erythropus are West 

 African and referable to the typical subspecies, except 

 Kuppell's leucoumbrinus, which will stand for the very similar 

 ^Soudanese and Abyssinian animal. 



Xerus erythropus chadensis, subsp. n. 



Similar in general characters to Upper Nile examples of 

 X. e. leucoumbrinus, but the colour much lighter throughout. 



