32 U.S. NATIONAL MUSEUM BULLETIN 275 



Giarabub. Representatives of both also occur farther east at Siwa 

 Oasis in the Western Desert of Egypt. In northern Egypt, the great 

 chain of depressions composed of the Wadi Natroun, Qattara Depres- 

 sion, and Siwa Oasis probably has acted as a dispersal corridor through 

 which members of these two subspecies have extended their range into 

 Libya. 



Saharan Desert Faunal Area 



The Saharan Desert Faunal Area comprises all of Libya south of 

 the Saharan Steppe Faunal Area. This faunal area is limited entirely 

 to the truly Saharan portions of Libya and is divisible into an eastern 

 Cyrenaican Desert Province and a western Fezzanese Desert Province. 



Owing to the insular distribution and relative isolation of popula- 

 tions of rodents in the Saharan Desert Faunal Area, a high degree of 

 endemism is found. Although no full species are restricted to this 

 faunal area, 11 of the 16 subspecies which occur here are endemic. 

 This high proportion of endemic subspecies is a most distinctive feature 

 of this area. 



The most widespread species of rodents in this faunal area include 

 Gerbillus gerbillus, Gerbillus campestris, and Jaculus jaculus. These are 

 all typical desert species and are common also in the steppe and littoral 

 desert regions of Libya. 



The Fezzanese Desert Province is confined in Libya to the Fezzan 

 but includes adjacent portions of southeastern Algeria and parts of 

 northern Niger and the Chad. This province is bordered on the north 

 and east by the mountainous barriers of the Hamada de Tinrhert and 

 the volcanic massifs of the Gebel es Soda and the Gebel el Harug el 

 Asued. It is limited on the west by the mountain complex of Tassil-n- 

 Ajjer and the Ahaggar Mountains of southeastern Algeria and on the 

 south by the Plateau de Mangueni of northern Niger and the Tibesti 

 Mountains of northern Chad. All these surrounding, rocky mountain- 

 ous areas provide unsuitable habitat for most species of rodents oc- 

 curring in the Fezzan. Genetic exchange with populations outside of 

 the Fezzan, therefore, has been of rare occurrence and a large number 

 of endemic subspecies have arisen. Endemic rodents in the Fezzanese 

 Desert Province are: Gerbillus gerbillus discolor; Gerbillus pyramidwm 

 tarabuli; Meriones caudatus amplus; Eliomys quercinus denticulatus; 

 and Jaculus jaculus arenaceous. 



The Cyrenaican Desert Province is limited to the central and south- 

 ern portions of Cyrenaica and includes the desolate areas of the Sand 

 Sea and Serir of Calanscio and the isolated oases of southern Cyrenaica. 

 This province is characterized also by a largely endemic fauna and has 

 restricted to it: Gerbillus gerbillus aeruginosus; Gerbillus campestris 

 patrizii; Jaculus deserti rarus; Jaculus deserti vastus; Jaculus jaculus 

 collinsi; and Jaculus jaculus cufrensis. 



