RODENTS OF LIBYA 157 



particularly Meriones libycus, Gerbillus eatoni, and Psammomys obesus. 

 These unusual rats are most abundant in the transitional 

 deserts which run roughly parallel to the more lush coastal plain. 

 They seem to prefer the flat, rock-strewn surfaces of the hamadas and 

 the margins of the shallow, dry watercourses which dissect them. In 

 these areas, the surface is covered with coarse pebbles and occasionally 

 with larger boulders, and the vegetative cover is usually sparse and 

 localized. The collecting localities near Rumia and Chicla in Tri- 

 politania are located on the broad uplands near the brink of the 

 coastal escarpment where vegetative cover is denser, and the ground 

 is rockier with occasional outcroppings of larger rocks. 



Setzer (1957, p. 60) reported the habitat near El Agheila as con- 

 sisting of a "rock shingle type of desert," and suspected that local, 

 terrestrial snails provided a source of food for fat-tailed sand rats. 



Genus Meriones Illiger 



The first records of members of this genus in Libya are those of 

 Thomas (1902, p. 8), who, reporting on specimens obtained by Edward 

 Dodson of the Whitaker Expedition to Tripoli (1901), referred 

 specimens from various localities in Tripolitania and the Fezzan to 

 Meriones shawi (Rozet) and Meriones schousboei (Loche). Thomas 

 noticed "characteristic differences" in the size of the auditory bullae 

 but mentioned that the two species were almost indistinguishable in 

 external characters and would probably prove to be "mutually 

 exclusive." He considered M. schousboei as the Barbary representative 

 of the Meriones erythrourus (Gray) group, the latter being widely 

 distributed throughout the Middle East and Southwest Asia. 



Later, Thomas (1919), in an effort to clarify the confusion of names 

 applied to this group, divided the genus into four groups based on 

 the relative size and shape of the auditory bullae and the suprameatal 

 triangle. Members of group "a" with large auditory bullae and large 

 suprameatal triangles included Meriones pelerinus Thomas, Meriones 

 crassus Sundevall, and Meriones pallidus Bonhote. Group "b," con- 

 sisting of animals with large auditory bullae but comparatively small 

 suprameatal triangles, included Meriones libycus Lichtenstein and M . 

 schousboei. Those possessing both small auditory bullae and triangles 

 formed group "c," which consisted of Meriones isis Thomas and M. 

 shawi. The last division, group "d," consisted of those types having the 

 smallest auditory bullae and included Meriones syrius Thomas, Meri- 

 ones charon Thomas, Meriones ambrosius Thomas, and Meriones 

 blackleri Thomas, whose ranges were confined to Asia Minor and 

 Southwest Asia. The majority of the above species were described as 

 new at this time. 



