1909,] COLLECTION OP MAMMALS FROM EGYPT, 795 



inundation, when it is forced to take refuge in the villages. Some 

 specimens procured on the southern shores of Lake Moeris in the 

 Fayum were indistinguishable from Cairo examples. 



AcoMYS CAHiRiNUS (Desm.), 



Mus cahirinibs Desm. Nouv. Diet. Hist. Nat. xxix. p. 70(1819). 



Acomys cahirimts de Wint. in Anders. Zool. Egypt, Mamm. 

 p. 282 (1902). 



This is the common House Mouse of Cairo, far outnumbering 

 Af'us musculus. A large series (86) was examined : they prove 

 very constant in coloration, and with the exception of the fingers 

 and toes they are of a uniform slaty blue all over. Slight traces 

 of white are sometimes visible on the breast and along the 

 median line. The sexes are alike in size and the average is : — 

 Head and body 101 mm. ; tail 105 ; hind-foot 18; ear 17. The 

 largest individual (a male) measured : — Head and body 109 mm. ; 

 tail 119 ; hind-foot 19 ; ear 19. 



Acomys russatus Wagn. 



Acomys russatus Wagner, Abh. Akad. Munich, iii. p. 195, 

 pi. 3. fig. 2 (1840) ; Tristram, Fauna Palestine, p. 11, pi. 3. fig. 1 

 (1884). 



I procured a single example of this species within half an hour's 

 ride of the Citadel on the Mokattam Hills, and it seems certainly 

 strange that it should not pi-eviously have been recorded from 

 Egypt. 



It is an extremely well-marked species, and may easily be 

 distinguished by the hairiness of the ears on both their inner and 

 exterior surfaces and by the colour of the under parts being of a 

 greyish white with no sharp line of demarcation from the colour 

 of the upper parts. In all other species of Acomys the ears are 

 naked and the under parts (except in A. cahirinus) are snowy 

 white divided sharply from the colour of the upper parts. 



The colour of the upper parts is a uniform reddish fawn, the 

 brown tips to each spine being so minute as not in any way to 

 affect the general colour. The feet are thickly covered with short 

 spines and the tail is well clothed with stiffish hairs. 



The shidl differs from that of its allies in having the snout 

 rather shorter and broader, the bullae considerably larger and thus 

 tending to constrict the basi- occipital and to make it more concave. 

 The most noticeable point, however, is the size of the teeth and 

 the length of the molar series, which latter measures 5 mm. as 

 against 4 mm. in the other species. A. nesiotis Bate has a molar 

 series of 4"5 mm. and in this measurement comes nearest to the 

 present one, but the whole animal is larger, so that the increase in 

 size of the teeth is merely in proportion to the general increase 

 in the size of the animal. In other respects the skull of nesiotis 

 agrees with that of dimidiatus. 



For many details of this group I am indebted to Mr. R. C. 



