210 U.S. NATIONAL MUSEUM BULLETIN 2 75 



extends farther dorsally into the supraoccipital bone. In external 

 measurements the populations from Egypt and Libya are comparable, 

 but, in color, the Libyan specimens are more uniform, whereas the 

 Egyptian specimens show a wide range of color, divisible generally 

 into two distinct color phases. 



The Libyan specimens differ significantly from representatives of 

 Acomys dimidiatus dimidiatus (Cretzschmar) form Feiran Oasis, Sinai, 

 in their smaller, more gracile skulls, more flattened braincases, and 

 narrower anterior palatine foramina. The foramen magnum, in the 

 Libyan specimens, is much more rounded dorsally and the foramina in 

 the pterygoid fossae are appreciably larger. In color, they are much 

 darker, gray as opposed to buff, and more uniformly colored. 



In cranial measurements, specimens from Cufra resemble those of 

 Acomys dimidiatus hunteri de Winton from the Eastern Desert 

 Governorate of Egypt and the Sudan, but differ markedly from the 

 latter in their darker color, smaller size, prominently rounded dorsal 

 surface of foramen magnum (as opposed to markedly flattened or 

 truncated in A. c. hunteri), and shorter anterior palatine foramina. 



Remarks. The series of spiny mice from Cufra Oasis is here referred 

 to Acomys cahirinus viator but with reservations. In color, specimens 

 from Cufra closely resemble two near topotypes of A. c. viator from 

 near Socna and Bir Fergian, Tripolitania. They are slightly smaller in 

 overall length but are of comparable size in all other external dimen- 

 sions. Unfortunately, the skull of the adult specimen from Bir Fergian 

 was lost, and the other specimen from near Socna is extremely young; 

 thus, cranial comparisons are not possible. Compared to measurements 

 of the type specimen of A. c. viator, as given by Thomas (1902) in the 

 original description, specimens from Cufra are slightly smaller in 

 greatest length of skull and have slightly wider interorbital breadths. 



It seems unlikely that the same subspecies would occur in such 

 widely separated geographic areas in Libya, such as Socna, El 

 Barcat, and Cufra, particularly since suitable habitat is sporadic and 

 localized. The referral of these specimens to A. c. viator must therefore 

 be considered provisional until such time as additional specimens of 

 A. c. viator are forthcoming and permit more accurate comparisons. 

 Spiny mice from Cufra represent geographic isolates, clearly distinct 

 morphologically from all other populations to the east, and probably 

 will prove also to be subspecifically distinct from A. c. viator. 



In the past, A. cahirinus and A. dimidiatus have been variously 

 regarded as either distinct species or the latter treated as a subspecies 

 of A. cahirinus. Ellerman and Morrison-Scott (1951) regarded the 

 smaller A. cahirinus purely as a commensal form and relegated the 

 larger and exclusively wild form (A. dimidiatus) to subspecific status 

 under A. cahirinus. Setzer (1959) recognized two species of spiny 

 mice as occurring in Egypt and Sinai; he considered A. cahirinus 



