RODENTS OF LIBYA 187 



Genus Psammomys Cretzschmar 



In the past, the taxonomy of the genus Psammomys has been almost 

 constantly in a state of confusion. Thomas (1902) was the first to 

 report on representatives of this genus from Libya and described 

 Psammomys tripolitanus as a new species based on specimens from 

 Bou Cheifa, Wadi Aggar, and Wadi Cheggar of northern Tripolitania. 

 He assigned specimens, which were much smaller in size and paler 

 in color, from Bu Ngem and the Wadi Wagis, Tripolitania, to Psam- 

 momys roudairei Lataste. The latter species was known from only two 

 immature types (type specimen and cotype) and had previously been 

 regarded by Lataste (1887) as a synonym of Psammomys obesus 

 Cretzschmar. Many years later, Thomas (1925) after examining more 

 specimens from near the type locality of P. roudairei in Algeria, once 

 again placed P. roudairei in the synonymy of P. obesus and proposed 

 the name Psammomys vexillaris for the small, pale-colored specimens 

 from Bu Ngem and the Wadi Wagis in Libya. 



Since that time, P. tripolitanus and P. vexillaris have been variously 

 regarded as full species (de Beaux, 1932; Zavattari, 1934) or either 

 one or the other regarded as subspecies of Psammomys obesus (Eller- 

 man, 1941; Ellerman and Morrison-Scott, 1951; Toschi, 1954). 

 Ellerman and Morrison-Scott, as well as Toschi, considered P. tri- 

 politanus as being synonymous with P. o. obesus and accorded P. 

 vexillaris only subspecific rank under this species. More recently 

 Setzer (1957), after examining two specimens from near El Agheila 

 and Gheminez, Cyrenaica, reinstated P. tripolitanus as a subspecies 

 of P. obesus and regarded P. vexillaris as a full species, based upon a 

 single specimen from Wadi Bey about 45 kilometers west of Bu Ngem, 

 Tripolitania. He considered the two forms as specifically distinct on 

 the basis of the following characters of the skull of P. vexillaris: 

 Supraorbital bead absent, temporal ridges markedly reduced, and 

 molars relatively as well as absolutely larger than in P. o. obesus. 



In addition to the above characters established by Setzer, this 

 specimen from near Bu Ngem differs strikingly from topotypes of 

 Psammomys obesus obesus from the Nile Delta in its much smaller 

 overall size, less robust and more gracile skull, proportionately larger 

 suprameatal triangles, more ventrally inflated auditory bullae, and 

 less developed parietal crests and postorbital processes. In color and 

 external characters, P. vexillaris differs markedly in having a much 

 shorter tail with a less extensive pencil, grayish rather than blackish 

 pinnae, greater suffusion of white on venter, white rather than 

 strongly buff-colored dorsal surfaces of hind feet, and much paler, 

 more subdued, dorsal color. 



