52 THE SPINY MICE OF BRITISH EAST AFRICA 
This specimen (No. 1477) is exactly similar to the type 
in general colour, but I have not been able to use it as a type, 
since the tail is badly broken. 
Type . — Adult. Original number 1481. Collected June 14, 
1918. 
This striking and distinct species is immediately dis- 
tinguished from A. Wilsoni by its very much longer tail and 
darker colour ; in general colour nubilus is darker than any 
of the other East African Acomys , with the exception of the 
slate-coloured Percivali. It is a little difficult to decide to which 
group this species belongs, and for the present it seems most 
satisfactory to regard it as a link between the large long-tailed 
ignitus group and the short-tailed Wilsoni. 
The following are the various forms of Acomys now 
recognised in British East Africa : — 
1. Acomys ignitus, Dollm., originally described from 
specimens collected by Mr. Kemp at Voi, has since been found 
by Mr. Percival at various localities between Voi and the 
coast. There are now before me specimens from the Tarn 
Desert and Witu which are undoubtedly true ignitus. On 
the west this species was found by Mr. W. P. Lowe on the 
Southern Guaso Nyiro and Narossura rivers in the Nyanza 
Province. 
2. Acomys i. Kempi, Dollm., has been recorded from many 
localities along the Northern Guaso Nyiro ; the type-locality 
of this form is the Chandler Falls. Mr. Percival has collected 
Kempi all along the river as far as the Lorian Swamp, and in 
the west he has found it at Baringo and on the Larrogie 
Mountains and Mathews Range. 
8. Acomys i. montanus, Hell., is only known from the 
specimens collected by Mr. Percival in the Marsabit District. 
4. Acomys Percivali, Dollm., was first found on the Northern 
Guaso Nyiro at the Chandler Falls. Since this discovery Mr. 
Percival has collected this conspicuous species on the Laikipia 
Plateau and on Mt. Urguess (Mt. Gargues). 
5. Acomys pulchellus, Dollm., type-locality Chandler Falls, 
Northern Guaso Nyiro, has been collected by Mr. Percival 
at Lasamis on the Marsabit Road ; a specimen from as far 
north as Mt. Nyiro seems also to belong to this species. 
