108 U.S. NATIONAL MUSEUM BULLETIN 275 



Representatives of this subspecies from El Gatrun on the eastern 

 margin of the Idehan Murzuch are paler in dorsal color than those 

 from elsewhere in the Fezzan. When specimens of Gerbillus gerbillus 

 become available from the Serir Tibesti and other regions to the 

 south, they may represent an undescribed subspecies to which the 

 specimens from El Gatrun will be referable. 



Gerbils from El Abiad, 55 kilometers west of Ubari, 75 kilometers 

 south -southwest of Serdeles, and 12 kilometers north of Ghat are 

 remarkably uniform in color and cranial characters. Apparently the 

 sandy beds of the Wadi el Agial, Wadi Irauen, and the Wadi Tenezoft 

 act as dispersal corridors which insure genetic uniformity among these 

 widely scattered populations. 



Members of this subspecies from the vicinity of Hun, Socna, and 

 Bir Fergian, Tripolitania Province, show many characters typical of 

 Gerbillus gerbillus psammophilous, whose range includes most of 

 Cyrenaica and the coastal areas of the Gulf of Sirte. In the degree of 

 inflation of the auditory bullae, breadth of the anterior palatine fora- 

 mina, and the size and shape of the posterior lacerated foramina between 

 the basioccipital and auditory bullae, they resemble G. g. psammophil- 

 ous, but in the majority of cranial characters, they are closer to G. g. 

 discolor to which they are here referred. For additional comments 

 regarding gene exchange with G. g. psammophilous, see under 

 "remarks" in account of that subspecies. 



Although this subspecies is characterized by generally darker, more 

 variegated dorsal color, individuals in the population range from uni- 

 form colors of pale, subdued tones to rather brilliant, ochraceous hues. 

 Partial albinism is also of occasional occurrence. In gerbils from Sebha 

 and Temenhint Oases of the central Fezzan, this broad range in dorsal 

 color is particularly striking. These oases apparently represent areas 

 in which the genetic character of the population is less rigidly fixed. 



These small gerbils are probably the most widely distributed rodent 

 in the Fezzan. They are most abundant near the periphery of the 

 oases where the palm groves are less dense and open sandy areas are 

 more widespread. In the Fezzan, G. g. discolor is sympatric with the 

 larger, and usually more abundant, Gerbillus pyramidum tarabuli. 

 Other rodents, such as Gerbillus amoenus, Jaculus jaculus, Meriones 

 caudatus, and Acomys cahirinus occur with G. gerbillus but usually 

 are far less abundant. 



The range of this subspecies, as far as is known, does not include 

 coastal Libya. In the coastal areas of northern Tripolitania, members 

 of the Gerbillus pyramidum group are the dominant gerbils. 



The term discolor, from the Latin meaning "of different color or 

 colors," is used for the subspecies name in reference to the variegated 

 character of the dorsal pelage. 



