3 1-4 On some new Forms of Otomjs. 



Otomys irrorcdus tropicalis, subsp. n. 



The northern strong-coloured form of 0. irroratus, with 

 seven lamina? to the last upper molar. 



Size slightly larger than in 0. irroratus. General colour 

 deep brown, nearest to " vandyke-brown " of Ridgvvay, very 

 different therefore to the grizzled grey of true South-African 

 irroratus. In each case the colour varies considerably, but 

 the general tone seems always darker in the northern animal. 

 Sides clearer brown. Belly slaty, with the tips of the hairs 

 buffy; in irroratus they are comparatively clear grey. Sides 

 of muzzle dark fulvous. Eyes without lighter rings. Ears 

 of medium length, well-haired, rather paler than the head. 

 Upper surface of hands and feet dark brown, the digits darker 

 than the metapodials. Tail less than half the length of the 

 head and body, well-haired, broadly black above, dull whitish 

 below. 



Skull apparently much as in true irroratus, but the nasals, 

 though very variable, tend to be more broadly expanded 

 anteriorly, and the interorbital space is commonly narrower. 

 Teeth as in irroratus, but the last upper molar with seven 

 laminee. 



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



Head and body 195 millim.; tail 93; hind foot (s. u.) 30; 

 ear 23. 



Skull : greatest length 43*5 ; basilar length 35 ; zygomatic 

 breadth 2r7 ; nasals 18x7*5; interorbital breadth 3*3 ; 

 palate length 19'5 ; palatal foramina 8'2 ; length of upper 

 molar series (crowns) 8*5 ; length of bulla 7*2. 



Hah. Eastern Tropical Africa, from British East Africa to 

 Nyasaland. Typical locality, western slope of Mt. Kenya, 

 British East Africa. Altitude 10,000 feet. 



Tyi^e. Old male. B.M. no. 0. 2. 1. 20. Collected 22nd 

 August, 1899, by Mr. H. J. Mackinder. 



The difference in general colour and in the number of 

 molar lamina? between northern and southern specimens of 

 this group has long been known, and it is quite time that a 

 name should be applied to the former. Examples from 

 Mashonaland vary in the number of the lamina?, and for this 

 reason I do not at present distinguish the East-African form 

 as a species, but only as a subspecies. The Mashona skins 

 are distinctly southern so far as colour is concerned, while 

 Nyasa ones are clearly northern. 



