62 U.S. NATIONAL MUSEUM BULLETIN 2 75 



Local differentiation of Libyan rodents indicates the presence of 

 four areas of potential endemism. These areas are the Cyrenaican 

 Plateau and coastal plain of northern Cyrenaica, the Gebel Nefusa, 

 the Fezzan, and Cufra Oasis. 



The distribution and composition of the Saharan (and Libyan) 

 rodent fauna has been profoundly influenced by the widespread 

 shifting of mammal populations during the Pleistocene. 



Owing to the similarities of the rodents of North Africa and South- 

 west Asia, and because of the high degree of endemism shown by 

 them, the Saharo-Sindien Faunal Region is here proposed as a new 

 zoogeographic region for this arid belt of steppe and desert. The 

 genera of rodents defining the Saharo-Sindien Faunal Region differ 

 as to origin and dispersal. The genera Allactaga, Jaculus, Calomyscus, 

 Meriones, Psammomys, and Rhombomys are clearly of Asian origin. 

 The genera Gerbillus and Acomys are apparently of African origin. 

 The genera Pachyuromys, Massoutiera, and Ctenodactylus probably 

 have developed in situ in North Africa. 



The arid region east of the Caspian Sea possibly has served as the 

 center of differentiation for most of the rodents comprising the 

 Saharo-Sindien Faunal Region. 



Interchange of Afro-Eurasian rodent faunas probably took place 

 at a time when the Nile River was less effective as a disperal barrier 

 than it is today. 



Systematic Treatment 



Plan of Treatment 



The phylogenetic arrangement of the taxonomic categories from 

 suborder to genus follows Simpson (1945). The species of each genus 

 and their component subspecies are arranged alphabetically. The major 

 genera are introduced by a detailed summary of their taxonomic 

 history, and in the case of Gerbillus, Meriones, and Jaculus, keys are 

 provided for the identification of the species. Owing to the lack of 

 standardization of vernacular names of North African rodents and the 

 inconsistency of their use by workers in the past, they have been 

 omitted as formal headings and are employed only in a general sense. 



The following procedure is employed in the accounts of species 

 and subspecies 



1. The currently accepted binomial name combination in agree- 

 ment with the "International Code of Zoological Nomenclature" 

 (1961) is followed on the same line by the name of the author. 



2. Original description: The original name is succeeded by the 

 name of the author, a reference to the original account, the date on 

 which the foregoing account was published, and the type locality in 

 parentheses. 



