292 Mr. R. C. Wroughton on 



to meet the almost equally well-marked lambdoid ridge. 

 Posterior palatal foramina long, longer than in valida, &c, 

 about as in dundasi. 



Dimensions of an adult male (measured in the flesh) : — 



Head and body 193 mm.; tail 208; hind foot 41; 

 ear (22). 



Skull : greatest length 52 ; basilar length 40 ; zygomatic 

 breadth 27 ; nasals 24 ; least intraorbital breadth 9 ; brain- 

 case breadth 19 ; diastema 15 ; anterior palatal foramina 9*5 ; 

 posterior palatal foramina 3 ; upper molar series 7 ; bullae 14. 



Mr. Kemp obtained a fine series of 27 specimens of both 

 sexes and all ages. In any key to the genus Tatera this 

 remarkable species would occupy a section by itself, charac- 

 terized by its uniformly black tail ; in all other known species 

 the tail is either dark above and pale below, as in all African 

 forms, or dark above and below and pale at the sides, as in 

 the Asiatic. 



Peters's second species, which I overlooked, is T. vicina. 

 There is a specimen from the type locality — Kitui — in the 

 National Collection, which may be accepted as representative 

 of that species. In my monograph (L c.) I described 

 T. mombasce from Mombasa. These two forms are un- 

 doubtedly closely related, if not identical. With such a 

 meagre description and only one, not very good, specimen, 

 it is not possible to come to a reliable conclusion. T. vicina 

 seems to have a well-marked tail-tuft, while mombasce has a 

 longer, more tapering tail with no long hairs towards the tip. 

 Both these forms are represented in the Voi collection. 



Finally, when my key was prepared, T. emini, characterized 

 by a band of hairs across the sole of the foot, immediately 

 behind the hallucal pad, occupied a section by itself. Since 

 then other species with this character have been described, and 

 quite recently (Ann. & Mag. Nat. Hist., Aug. 1910, p. 222) 

 Mr. Thomas has established the genus Taterillus to receive 

 them. There is a new form among the Gerbils from Voi, and 

 in comparing it with specimens from the Nile Valley it 

 appears that a series of specimens obtained at Dug-dug in the 

 Bahr-el-Ghazal by Mr. A. L. Butler represents a form 

 distinct from emini, its near neighbour. 



Thus there are now six species known of the genus 

 Taterillus, which may be arranged in a key as follows: — 



A. Size larger. 

 a. Colour darker. 



a'. Head and body 140 mm. ; hind foot 30 ; 

 skull length 36 ; brain-case 14 ; upper 

 molars 5 - 2. General colour " Mars- 

 brown." (Wadelai.) Taterillus emini, Thos. 



