460 Mr. O. Thomas on 



zygomatic breadth 18"2 ; breadth of braiii-case 15'3 ; ante- 

 rior palatine foramina 7*2 ; posterior palatine foramina 43 ; 

 upper molar series 5'4. 



Hah. and Type as above. 



This gerbil is most like the Soudanese T. hutJeri^ Wrought., 

 being distinguished from T. gracilis by its greater size and 

 from T. lacustris by its darker colour, these being the only 

 West-African species hitherto known. 



The Museum also contains a young specimen of the same 

 species collected at Tola by Mr. G. W. Webster. 



8. Arvicanthis mordax, sp. n. 



S. 3, 11 (young) ; ? . 12. Panyam, 4000'. 



Near A. rujinus, Temm., but greyer and teeth larger. 



Size large, as in A. rujinus. General colour decidedly 

 greyer than in rujinus, the head and fore-back more bufly 

 than " drab-grey," the tips of the hairs cream-buff, their 

 blackish slaty bases showing through. Hind-back and rump 

 gradually approaching " russet." Base of tail russet. Under 

 surface dull greyish, the tips of the hairs varying from 

 greyish white to drab. Hands and feet dull buffy. Tail 

 more heavily haired than in rujinus ; blackish above, buffy 

 on sides and below. 



Skull very similar to that of A. rujinus, but somewhat 

 greater in zygomatic spread, the length being about the same. 



Incisors, as in A. rujinus, very broad and heavy. Molars 

 markedly broader than in that species. 



Dimensions of the type (measured in flesh) : — 



Head and body 164 mm. ; tail 147 ; hind foot 34; ear 22. 



Skull: greatest length 40; condylo-incisive length o8'2 ; 

 zygomatic breadth 20"3; nasals 15-3; interorbital breadth 6'1 ; 

 palatilar length 18*3 ; palatal foramina &2 ; upper molar 

 series TQ ; breadth of m^ 2"4. 



Hab. as above. 



Ty^^e. Old female. B.M. no. 11, 3. 24. 11. Original num- 

 ber 12. Collected 14th September, 1910. 



This is no doubt the N. -Nigerian representative of 

 A. rujinus, from which it differs by its greyer colour and 

 larger molars. 



A specimen of it, without skull, was also obtained during 

 the Alexander-Gosling Expedition by the late Capt. Boyd 

 Alexander at Ibi, on the Benue, in 1904. 



