220 U.S. NATIONAL MUSEUM BULLETIN 2 75 



I have not examined these specimens from the Tripolitanian Gebel, 

 but because the descriptions of these specimens given by Klaptocz 

 and Toschi agree quite closely with the original description of Eliomys 

 lerotinus tunetae (= Eliomys quercinus tunetae), and on account of 

 geographic proximity, they are here referred to E. q. tunetae. 



Family Dipodidae 

 Genus Jaculus Erxleben 



Jerboas in Libya show varying amounts of geographic variation 

 depending upon the species. Jaculus jaculus has undergone the 

 greatest amount of differentiation associated with geographic dis- 

 tribution. The other two species, occurring in Libya, Jaculus orientalis 

 and Jaculus deserti, are less variable morphologically. The latter two 

 species are represented by samples of relatively small size and, in 

 some cases, the full range of variation for any given character may 

 not be accurate. In jerboas, as with gerbils, geographic variation is 

 usually not manifested by ordinary meristic and quantitative char- 

 acters, such as external measurements and cranial indices, but is 

 indicated by more subtle, qualitative differences, which do not 

 ordinarily lend themselves to measurement or statistical analysis. 

 The most important of these characters associated with geographic 

 variation include differences in color, shape and configuration of the 

 auditory bullae, angularity and massiveness of the skull and zygo- 

 mata, and changes in the degree of doming of the braincase. 



a' 



Figure 48. — Statistical comparison of length of ear of the species of Jaculus: A, /. deserti; 



B, /. jaculus; C, J. orientalis. 



