and allied East- African Species. 341 



1827. Ilypudceua nilotkus, Brants, Muizen, p. 87. 



]827. Mns variegatus, Brants, Muizen, p. 102. 



1829. Echimys fiiloticnx, Geoff, et And. Descr. ^figypte, ii. p. 734 



("Echimys d'Egypte,"' Atlas, pi. v. fig. 2). 

 1842. Anncanthis niloticus, Lesson, Nouv. Tal). Reg. Anim. p. 147. 



1842. Mus discolor, Wagner, Arch. Naturg. i. p. 9. 



1843. Isomys variegatus, Suudevall, Vet.-Ak. Ilandl. p. 220. 

 Isomys variegatus, var. major, id. ibid. 



A very large dark olive-coloured species, with a large 

 massive skull. 



Size of body and hind foot larger than iu any of the allied 

 forms*. Tail shorter than body. General colour olive- 

 buff, heavily lined with black, the general effect darker than 

 in the ahyssinicus group. Dorsal stripe generally ill-defined, 

 but in some individuals dark and quite as prominent as in 

 ahyssinicus. Flanks rather paler and yellower than back. 

 Backs of hands and feet buff-coloured. Under surface of 

 body dirty greyish white, tinted with buff. Ventral surface 

 not sharply marked from flanks. Hairs of belly with dark 

 slate-grey bases and whitish tips. Tail short, colour much 

 as in testicularis, rathe*" darker sbove. 



Skull larger and heavier than in any of the other forms 

 dealt with in this paper. Zygomatic region very broad^ 

 especially so in the squamosal portion. Occipital breadth 

 greater than in testicularis. Palatal cavities long, but nob 

 proportionally broader than in the smaller species. Auditory 

 bullae rather larger than in testicularis. Incisors broad and 

 heavy. Molars rather larger than in the Sennaar species, 

 especially m^. 



Dimensions in millimetres (measured in the flesh) : — 



Average of 



10 adults. Max. Min. 



Head and body 174 195 160 



Tail 139 148 180 



Hind foot 35 38 33 



Adult skull: greatest length 40 mm. ; basilar length 34; 

 condylo-incisive length 39; zygomatic breadth 21*5; inter- 

 orbital constriction 6; squamosal breadth of cranium 16; 

 length of nasals 15-5; palatilar length 19 ; length of palatal 

 foramina 9 ; alveolar length of upper molar series 8. 



Many adult skulls of niloticus are rather smaller than the 

 above dimensions, in some cases the greatest length being 

 only 38 mm. 



* A. rex, Thos., is not included in this paper, as its affinities are very 

 doubtful. In size it is far greater than any of the species mentioned here 

 (head and body 212 mm., tail 176). 



Ann. cC- Mag. N. Uist. Ser. 8. Vol. viii. 23 



