RODENTS OF LIBYA 231 



For comparison with Jaculus deserti fuscipes, see account of that 

 subspecies. 



Remarks. Jaculus deserti vastus can easily be distinguished from all 

 other small Libyan jerboas by its much larger body size, markedly 

 longer tail and hind feet, and much greater suffusion of buffy hairs 

 on the forelegs, sides, and venter. 



Although this specimen doubtless belongs to the "deserti" group 

 of jerboas, the above differences are of sufficient magnitude to warrant 

 the designation of a new species. Owing to lack of adequate material 

 it is deemed better, however, to limit the category to subspecific 

 rather than specific rank. 



The type specimen is the only record of occurrence for this subspecies 

 in Libya. The above specimen was obtained from the rocky, denuded 

 margins of the Wadi er Rueis at a point where it emerges from the 

 higher parts of the Gebel el Harug el Asued (Black Gebel). Volcanic 

 extrusions are widespread in this area and in many places encroach 

 upon the Wadi. Vegetative cover is very limited and is composed 

 primarily of acacias, woody shrubs, and hardy grasses. 



This large jerboa probably has a much wider distribution in Libya 

 than the present study would indicate, and its range doubtless in- 

 cludes the entire massif of the "Black Gebel" and the low-lying pe- 

 ripheral areas wherever suitable habitat occurs. 



Jerboas inhabiting the Gebel el Harug el Asued are effectively 

 isolated from the ranges of other subspecies of Jaculus deserti in 

 Libya, Gene exchange with these other populations is accordingly of 

 infrequent occurrence and genetic fixation and differentiation have 

 thus progressed rapidly. Owing to the remoteness and consequent 

 inaccessibility of central Cyrenaica, additional specimens of this 

 unique jerboa will probably long be wanting. 



The name vastus, from the Latin meaning empty and waste, alludes 

 to the remote regions inhabited by jerboas of this subspecies. 



Jaculus jaculus (Linnaeus) 



M us jaculus Linnaeus, Syst. Nat., 10th ed. p. 63, 1758 ("In Arabia, Calmukia"; 

 Giza Pyramids, Egypt [G. Allen, 1939]). 



General distribution of species. Iraq, Syria, Lebanon, Israel, 

 Jordan, Saudi Arabia, North Africa southward through the Sahara 

 including Sudan, Chad, Niger, Mauritania, and Spanish Sahara. 



Distribution in Libya. Widespread through the coastal and in- 

 terior areas of Cyrenaica, Tripolitania, and the Fezzan. 



Distribution of the subspecies in Libya. 



Jaculus jaculus arenaceous. Fezzan: Oases and connecting wadis. 



Jaculus jaculus collinsi. Cyrenaica: Gialo and Tazerbo and the 

 intervening Serir of Calanscio. 



