RODENTS OF LIBYA 175 



as separate species, and the above mentioned sympatry is to be 

 expected. 



I have not examined Toschi's specimens, but judging from his 

 measurements, they most likely belong to Meriones caudatus luridus 

 and not to Meriones libycus libycus. This does not preclude the pos- 

 sibility that the latter species occurs at Giarabub. Representatives 

 of both species occur sympatrically along the northern Cyrenaican 

 coast and doubtless are sympatric throughout coastal Egypt. 



One specimen of M. c. luridus, 325586, from 11 kilometers east of 

 Ain el Gazala on the northern Cyrenaican coast is almost identical 

 in color to topotypical Meriones caudatus confalonierii from near El 

 Agheila farther west in Libya. This is the only evidence of intergrada- 

 tion with populations of M. caudatus to the west. The high tablelands 

 of the Cyrenaican Plateau, the massif of the Gebel Achdar, and the 

 marked reduction of the coastal plain apparently act as deterrents 

 to gene flow between members of this subspecies and those farther 

 west. Meriones caudatus luridus probably has greater affinities with 

 jirds in western Egypt. Its range probably includes Giarabub Oasis 

 and all of the inland hamadas south of the Cyrenaican Plateau in 

 Libya, the Libyan Plateau of extreme northwestern Egypt, and the 

 extensive low-lying areas of Siwa Oasis, the Qattara Depression, and 

 the Wadi Natroun in Egypt. The barren vastness of the Serir of 

 Calanscio and the Sand Sea of Calanscio, in Libya, and the desolate 

 Western Desert in Egypt apparently limit the southward distribution 

 of these jirds. 



This subspecies is known from comparatively few specimens and 

 the full extent of its variation is unknown. Two specimens, 302316 and 

 302317, from Giarabub, however, are noticeably more orangish in 

 dorsal color and lack the typical yellowish-buff color of the tail. A 

 large series from south of Bir el Gobi, most of which are subadults, 

 are constant in showing this pale yellowish dorsal color. 



Ecological observations. In Libya, this subspecies is confined 

 primarily to the hamadas and sandy deserts of the interior, but the 

 collecting sites 11 kilometers east of Ain el Gazala and 10 kilometers 

 southwest of Fort Capuzzo are less than 15 kilometers from the 

 Mediterranean coast. In coastal areas, members of this subspecies 

 occur together with those of Meriones libycus. The extent of the range 

 of the latter species farther inland has not yet been ascertained, but 

 the two species are probably sympatric throughout all of northeastern 

 Libya and northwestern Egypt. 



These jirds have similar habitat preferences to populations of M. 

 c. caudatus and M. c. confalonierii in western Libya, all having a 

 decided predilection for sandy areas. The habitats at the following 

 localities in Cyrenaica are characterized as follows: 11 km E Ain el 



