26 U.S. NATIONAL MUSEUM BULLETIN 2 75 



with a discontinuous cover of small shrubs, primarily Artemisia. 

 The large grass Stipa tenacissima, known locally as "esparto" grass, 

 is harvested and exported on a fairly large scale in some parts of coastal 

 Libya. 



Grass cover of the Arislida type is dominant in all desert areas of 

 Libya. The Aristida plumosa L.-A obtusa Del. -A acvtifolia Trin. and 

 Rupr.-A ciliata Desf.-A pungens Desf. "type" is typical of the pre- 

 Saharan or transitional desert area of northern Tripolitania and 

 Cyrenaica. These grasses are also associated with a steppe type of 

 vegetation consisting of small, scattered groups of acacia and desert 

 shrubs. Stipa lagascae, S. capensis Thunb., and S. barbata Desf. are 

 present but are not common in this zone. 



In the Libyan Sahara, where the annual rainfall is less than two 

 inches, the Aristida spp.-Panicum turgidum Forsk.-Lasiurus hirsutus 

 Boiss.-Pennisetum divisum (Gmel.) Henrard "type" of grass cover is 

 most characteristic. In the Sahara, these grasses are associated with 

 scattered acacias and shrubs including such genera as Anabasis L., 

 Haloxylon, and Cornulaca. Frequently vast areas are devoid of vegeta- 

 tion, and only an ephemeral cover of grasses and herbs appears follow- 

 ing a period of rainfall. 



Mammalian Faunal Areas 



Libya has three primary faunal areas based on the distribution of 

 the rodent fauna. These areas coincide roughly with the major physi- 

 ographic, vegetative, and climatic features of the country. These 

 faunal areas are divisible into regional provinces according to the 

 kinds of rodents most typical of each. These areas (with the provinces 

 in parentheses) are: Mediterranean (Coastal Plain, Cyrenaican 

 Plateau) ; Saharan steppe (Transitional Desert, Tripolitanian Gebel) ; 

 and Saharan Desert (Cyrenaican Desert, Fezzanese Desert). 



Each faunal area is characterized by certain species (or subspecies) 

 restricted to it or which occur only marginally in an adjacent faunal 

 area. Members of a given subspecies are usually confined to the same 

 province, but occasionally representatives of a widely ranging sub- 

 species can occur in both provinces of a faunal area. Representatives 

 of genetically plastic subspecies frequently occur in more than one 

 faunal area, but these are exceptional cases. 



Owing to the diverse topography of Libya, a greater number of 

 mammalian faunal zones could be expected. The aridity of the Saharan 

 interior apparently renders most areas unfit for life, and as a result, 

 only the most adaptable species of rodents are able to survive. Be- 

 cause the Saharan portion of Libya comprises most of the land area 

 and because of the widespread distribution of most of the desert 

 species, the faunal areas are correspondingly large. 



