340 Mr. G. DoUraan on Arvicanthis abyssi;iicus 



Face and head quite as dark as back ; ocular rinG:3 and tip of 

 nose orange. Dorsal stripe practically absent, a faint sugf^es- 

 tion of a median line visible under certain conditions of 

 illunnnation. Flanks paler and greyer than back, the pule 

 greyish buff-colour gradually merging into the light under 

 surface. Backs of hands and feet brownish, washed with 

 buff. Ventral surface of body light greyish white, faintly 

 tinted with buff, the coloration irregular, as in niloticns. 

 Hairs of belly with slate-grey bases and light tips. Tail 

 short and well covered with hairs; dark blackish brown 

 above, dirty buff-coloured below. 



Skull like that of testicu/ari's centraUs ; supraorbital ridges 

 more developed and with longer palatal foramina. 



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



Head and body 155 mm. ; tail 143 ; hind foot 33 ; ear 17. 



Skull : greatest length 35*4 ; basilar length 29*2 ; con- 

 dylo-incisive length 33"0 ; zygomatic breadth 17*2; inter- 

 orbital constriction 5 ; squamosal breadth of brain-case 14 ; 

 length of nasals 13'2 ; palatilar length 15'8; length of 

 palatal foramina 8 ; alveolar length of Uj)per molar series 7*2. 



Hah. Kaka, north of Fashoda, Soudan. 



Type. Adult male. B.M. no. 1. 8. 8. 50. Original num- 

 ber 35. Collected on April 23rd, 1901, and presented to 

 the 15ritish Museum by R. M. Hawker, Esq. 



This species is represented in the Museum collection by 

 three specimens — two from Kaka and one from Fashoda ; 

 they all present the same exceedingly dark-coloured pelage, 

 and are quite unlike any of the testicular is group. In general 

 characters this form appears to be intermediate between 

 niloticus and tesiiculai'is, possessing the short tail and general 

 colouring of niloticus and with cranial characters more like 

 those of lesticularis. It is at present impossible to deciiie 

 the exact relationship of this new species to the other forms 

 of Arvicanthis inhabiting the Nile Valley ; jU'obably it is 

 more nearly allied to testicuhvis than to the Egyptian 

 species. In general colour luctuosus is not unlike some of 

 the northern races of ab//ssinicus, such as rubescens ; but on 

 account of the great diiferences in the general dimensions 

 and cranial measurements it cannot be considered as belonging 

 to the abi/ssinicus group. 



(o) Ari'icantJiit! niloticus, Desm. 



1803. Lemtnus 7iilofirus, E. GeolV. Cat. >Iu?. Paris (noiu. niul.). 



1822. Arvicola niloficm, L)esulal•o^<t, Eucy. M(5tliod., Mamiu, Supvl. 



p. 281. 



1823. Hijptuhrm rariei/altis, Licbt. Verz. Doubl. Berlin, \\ 2. 



