388 Mr. O. Thomas on neio Ground- Squirrels 



General dorsal area between "pinkish bufF^' and "buff," 

 liglitening on the limbs to " cream-buti/' Head and fore- 

 back less uniform, more lieavily lined with blacki.sii. Inter- 

 mediate blind between the white lateral line and the white of 

 the belly darker than the general colour, more or less mixed 

 with blackish. Under surface very short-haired, partly 

 naked in the axillary and inguinal regions, white. Upper 

 surface of hands and feet cream-buff. IShort-haired part of 

 tail darker buffy. Long hairs of tail, as seen from below, 

 buff basally, occasionally approaching ochraceous buff, then 

 cream-buff, with a subterminal ring of black and a broad 

 cream-buff tip. In X. e. leucoumbrinus the basal part of 

 the tail-hairs is ordinarily "ochraceous buff^' or even 

 " ocliraceous." 



Skull apparently quite as in leucoumbrinus, the posterior 

 premolar proportionally large; rounded-quadrangular, not 

 small as in the East-African species. 



Dimensions of the type (measured in the flesh) : — 



Head and body 2G2 mm. ; tail 240; hind foot 63. 



Skull : greatest length 61"7 ; basilar length 49 ; zygomatic 

 breadth 33 ; palate lengtii from henselion 303 ; front of 

 large premolar to back of m^ 11'3; breadth of large pre- 

 molar 3*5. 



Hah. Yo, Lake Chad. 



Type. Adult male. Original number 44. Collected 11th 

 October, 1904, and presented by Capt. G. B. Gosling. 

 Four specimens. 



Xerus erythroj)us lacustris, subsp. n. 



Colour darker than in any of the allied forms, the back 

 heavily blackened, so as nearly to matcli liidgway's "mummy- 

 brown." Crown still darker, glossy blackish, speckled with 

 buffy. Area below white lateral line broader than usual, 

 finely speckled blackish. Under surface even more thinly 

 haired than usual, dull buffy whitish along the middle line, 

 the sides of the belly buffy, as are the inner sides of the 

 limbs and the upper surface of the hands and feet. Forearms 

 dark ochraceous clay-colour. Hairs of upper side of tail 

 black at their bases, those of the lower side ochraceous buff 

 basally. 



Skull with the large premolars cliaracteristic of A', erij- 

 iliropus, contrasting in this respect with the geographically 

 allied X. microdon. 



Dimensions of the tvpe : — 



Head and body .30;<nim. ; tail 240 ; Innd font 64. 



