180 U.S. NATIONAL MUSEUM BULLETIN 2 75 



a synonym of Meriones crassus crassus (Ellerman and Morrison-Scott, 

 1951 and Toschi, 1954). More recently, Setzer (1957) reinstated M. c. 

 tripolius as a valid subspecies of M. crassus and assigned specimens 

 from near Socna and Bir Fergian, Tripolitania, to it. He stated that 

 these jirds from Libya were markedly paler and had smaller skulls 

 with particularly less inflated posterior portions of the auditory bullae 

 than typical specimens of M. c. crassus from Sinai. Thomas (1919), 

 in the original description of Meriones pallidus tripolius, said that it 

 was very near to Meriones pallidus (= Meriones crassus pallidus), of 

 the Sudan, but with smaller auditory bullae and slightly darker 

 dorsal color. 



Throughout the known range in Libya, populations of these jirds 

 are remarkably uniform in cranial characters and dimensions. Jirds 

 from several localities in the Fezzan clearly belong to this subspecies 

 but differ from topotypes of M. c. tripolius from farther north in 

 Tripolitania in having slightly more gracile skulls, more delicate 

 zygomata, and in being slightly smaller in external dimensions. In 

 color, all Libyan representatives of this subspecies are inseparable. 

 Two specimens, a very old male (BM, no. 34.8.2.64) and an old female 

 (BM, no. 34.8.2.65) from El Golea, Algerian Sahara, are comparable 

 in color and external measurements to the specimens from Libya 

 but are noticeably larger cranially. This larger size of the Algerian 

 specimens may result from increased angularity and thickening of the 

 skull attributable to extreme old age. 



Ecological observations. In Libya, these jirds are represented 

 by comparatively few specimens from Tripolitania and the Fezzan 

 and are unknown from Cyrenaica. Several days of intensive trapping 

 at the oases of Brach and Edri in the Fezzan produced only two 

 specimens, both from the hamada-like plains several kilometers 

 distant from the palm groves and sand of the oases proper. Near 

 Ghat and Ubari they inhabited the margins of shallow wadis that 

 dissected the desolate, flat hamada. At all these collecting sites, vegeta- 

 tive cover was reduced to occasional bunches of dry grasses and 

 scattered acacias. One evening in January, while I camped on the 

 barren plain 26 kilometers north of Goddua, Fezzan, a single male 

 specimen, 322693, was captured alive when it approached to within 

 a few feet of the lantern. Visible vegetation at this campsite was 

 entirely lacking except for a distant solitary acacia tree. These hardy 

 rodents seem to prefer the more barren hamadas and sparsely vegetated 

 wadis located some distance from oases and were never collected 

 from dunes or sandy areas within palm groves. In the latter habitats, 

 however, the larger, more bushy-tailed Meriones caudatus is rather 

 common. Because of their preference for these marginal habitats, 

 specimens of M. crassus are obtained only rarely and are poorly 



