534 PROCEEDINGS OF THE XATIOXAL MTSEUM vol. ice 



Measurements: An adult male and an adult female from Gilo. 

 Imatong Mountains measure, respectively, as follows: Length of 

 head and body 119, 125; length of tail 69, 75; length of hind foot 22, 

 22; length of ear 11. 13; condyloincisive length of skull ?, 28.4; 

 posterior edge of M^ to front of incisor 14.2, 14.0; crown length of 

 upper toothrow 4.8, 4.8; greatest width across zygomatic arches 

 15.2, 14.5: least interorbital width 5.9, 5.8; length of nasals 11.6, 

 13.0; width of rostrum at level of antorbital foramen 3.5, 3.5; width 

 across M--M^ 6.7, 6.6. 



Remarks: This species is difficult to distinguish from L. aquilus 

 in all of the specimens examined. In general, sikapusi is darker in 

 color than is aquilus. In addition to the darker dorsal color, the 

 ratio between the width of the anterior ends of the auditory bullae 

 and the width of the posterior choanae averages about 60 percent, 

 which means that the choanae are narrower in proportion to the 

 space between the bullae. This same ratio in aquilus is in the neigh- 

 borhood of SO percent. The coloration of the belly is extremely 

 variable in both species and apparently is no criterion for sepai-ating 

 the two kinds. 



The amount of cranial variation between individuals of the two 

 species is so great that only averages may be used to determine the 

 correct allocation of specimens. 



Acomys albigena Henglin 



Acomys albigena Heugliii, Reise in Xordost-Afrika, vol. 2. p. 68, 1877. (Bogos 

 Country, Abyssinia.) 



Specimexs Examined: Four, all in BM, from Gallabat. 



Measurements: An adult male from Gallabat measures as foUows: 

 Length of head and body 94; length of tail 100; length of hind foot 19; 

 length of ear 16; greatest length of skull 30.0; cond^'loincisive length 

 26.7; length of anterior palatine foramina 7.1 ; crown length of upper 

 toothrow 5.0; least interorbital width 4.7; width of rostrum at level 

 of antorbital foramen 3.1; lengih of nasals 11.9; greatest width 

 across zygomatic arches 13.4. 



Remarks: This species is darker in color than any normally colored 

 Acomys in the Sudan. There is a blackish stripe along the mid-dorsal 

 line shading over the sides into a dark reddish buff. Belly, hands 

 and feet are pure white. The tail, instead of being rather uniformly 

 colored, as in other kinds, is dark above and white below, thus pre- 

 senting a bicolored aspect. 



