58 U.S. NATIONAL MUSEUM BULLETIN 2 75 



evidence of an Asian origin for the family Dipodidae and the two 

 genera occurring in Africa. 



The genus Meriones is clearly of Asiatic origin and probably repre- 

 sents a recent arrival of the Eurasian fauna into North Africa. Mem- 

 bers of the genus Meriones (jirds) are widely distributed in North 

 Africa in Egypt, Libya, Algeria, Tunisia, and Morocco but are con- 

 fined more to the northern portions of these countries. In Asia, several 

 species belonging to this genus are widely distributed in parts of 

 Transcaucasia, Russian Turkestan, Chinese Turkestan, Iran, Afghani- 

 stan, Baluchistan, and occur as far east as Manchuria and Mongolia. 



The genus Tatera, although unknown from the entire North African 

 coast and the Sahara proper, occurs extensively in Southwest Asia as 

 the monotypic Tatera indica Hardwicke. In Africa south of the Sahara 

 the genus is known polytypically. This hiatus in distribution of the 

 genus is a zoogeographical enigma which is not readily soluble. 



Africa may have served as the center of dispersal for the genus 

 Tatera, or the genus may represent a comparatively recent invasion 

 into Africa. The static nature of the genus in Asia, however, may be 

 the result of prolonged isolation of a peripheral isolate which shows 

 signs of genetic impoverishment and evolutionary decline. A static 

 gene pool is indicated by the maintenance of a single monotypic 

 species over such a large geographic area. The fact that in many parts 

 of the range of Tatera indica it is closely associated with human 

 agriculture suggests that this Asian species has indeed lost some of its 

 original genetic variability. 



In view of the extreme discontinuity in the range of the genus 

 Tatera, the Asian and African complexes must have become isolated 

 early in the Tertiary and have since evolved independently. 



The greater number of African species of Tatera, the more variable 

 nature of the populational gene pool, and the general similarity of its 

 range to those of other genera thought to have evolved in Africa, seem 

 to favor an African center of origin for the genus Tatera, but until the 

 fossil record provides something more conclusive, I prefer to regard 

 the geographic origin of Tatera with reservations. 



In the preceding pages, discussion has dealt with those genera 

 common to both the Saharan and Asian portions of the Saharo- 

 Sindien Region. Other genera characteristic of this newly proposed 

 zoogeographic region are confined either to the Saharan or Asian 

 portions. 



The family Ctenodactylidae , which comprises the genera Cteno- 

 dactylus, Massovtiera, Pectinator Blyth and Felovia Lataste, is proba- 

 bly the most unusual Saharan family. The genera Ctenodactyhts and 

 Massoutiera are exclusively Saharan, whereas Pectinator and Felovia 



