RODENTS OF LIBYA 179 



larger than those of M. c. crassus and, by inference, must be markedly 

 larger than those of M. c. tripolius in every detail. 



Meriones crassus can be distinguished easily from both Meriones 

 libycus and Meriones caudatus by larger and more posteriorly inflated 

 auditory bullae, larger suprameatal triangles with open posterior 

 processes rather than closed or closely approximating as in M. libycus 

 and M. caudatus, shorter tail, and generally paler, more uniform 

 dorsal color. 



Remarks. Setzer (1961) described Meriones crassus perpallidus from 

 Cairo- Alexandria Road, 4 kilometers from Cairo, Egypt, and stated 

 that it differed from representatives of Meriones crassus tripolius by 

 paler dorsal color, larger, more massive skull, wider, shorter rostrum, 

 and more posteriorly inflated auditory bullae. When paratypes of 

 these two subspecies are compared, however, M. c. tripolius can be 

 most easily distinguished from M. c. perpallidus by darker dorsal color, 

 with stronger suffusion of brownish hairs, and by markedly smaller 

 size of external dimensions. Paratypes of M. c. tripolius also have 

 slightly larger and more massive skulls, rather than smaller skulls 

 as stated by Setzer, and the mastoidal portion of the auditory bulla 

 is less inflated posteriorly. The breadth and length of the rostra do not 

 differ appreciably in paratypes of M. c. tripolius and M. c. perpallidus. 



When Setzer described M. c. perpallidus, he had only a few specimens 

 of M. c. tripolius from Tripolitania and apparently did not examine 

 typical specimens of M. c. tripolius from the Gebel Limhersuk. In the 

 present work, paratypes of both subspecies are at hand, some additional 

 characters by which these two subspecies differ are noted, and some of 

 the differences set forth by Setzer are not apparent. 



Thomas (1902) assigned specimens obtained by Edward Dodson in 

 1901 from several localities in Tripolitania and the Fezzan to Meriones 

 schousboei Loche. In a later paper (1919), using these same specimens, 

 he described Meriones pallidus tripolius (= Meriones crassus tripolius) 

 with the type locality at Gebel Limhersuk, Tripolitania, and named 

 Meriones libycus caudatus from Tamari-Fergian, Tripolitania. He did 

 not ascribe a specific range to either species, however, and in no way 

 indicated to which of the above species the specimens from the 

 Fezzan might be referred. Many years later, Chaworth-Musters and 

 Ellerman (1947) assigned these Fezzanese specimens to Meriones 

 crassus. 



Since Thomas described Meriones pallidus trijwlius ( = Meriones 

 crassus tripolius) in 1919, this subspecies has had an uncertain status. 

 It was first treated as a subspecies of Meriones libycus (Ellerman, 1941) , 

 later considered as a subspecies of Meriones crassus (Ellerman, 1947 

 and Chaworth-Musters and Ellerman, 1947), and finally regarded as 



