72 U.S. NATIONAL MUSEUM BULLETIN 275 



All specimens from Cyrenaica are either topotypes or near topotypes 

 of M. mustersi. Those from the coastal plain near Tocra, however, are 

 the farthest from the type locality, but two specimens are clearly 

 immature and are unsuitable for comparative purposes. The third is 

 of questionable adult status but is near or of comparable age to those 

 specimens with which it is being compared from Merg (= Barce) and 

 El Faidia. The specimen from Tocra is identical in color to M. mustersi. 

 In cranial characters it resembles rather closely a topotype of M. 

 mustersi from Barce but differs in slightly smaller size of skull and 

 external dimensions, shorter and narrower anterior palatine foramina, 

 slightly smaller pterygoid foramina, and slightly more inflated 

 mastoidal portions of the auditory bullae. 



From the specimen from near El Faidia, this specimen from near 

 Tocra differs in the same characters as set forth above, except the two 

 specimens are comparable in the length of the anterior palatine 

 foramina. 



These differences between the voles of the coastal plain and those 

 from the higher slopes of the plateau are too slight to suggest sub- 

 specific differences and indicate that M. mustersi is a monotypic 

 species whose range includes all of the Cyrenaican Plateau and the 

 adjacent coastal plain wherever suitable habitat occurs. 



Ecological observations. The three localities in Cyrenaica 

 where voles are known to occur differ markedly in the character of 

 the habitat. The type locality at Barce, according to Hinton (1926), 

 is at an altitude of 300 meters and in a basin of interior drainage 

 about 20 miles from the coast. Microtus inhabited open burrows with 

 well marked "runs" in the cornfields. The ground was described as 

 being "hard-baked." Near El Faidia, Setzer (1957) described the 

 terrain as hilly and rocky, and a single specimen was obtained from 

 the moist north-facing slope where mosses were growing. This locality 

 is significantly higher in elevation than the Barce Valley and is near 

 the highest point of the Cyrenaican Plateau. In contrast to the high 

 valleys and mountain slopes near Barce and El Faidia, the site near 

 Tocra is located on the lowest level of the coastal plain about one-half 

 kilometer from the Mediterranean Sea. This particular portion of the 

 coastal plain has a dense vegetative cover consisting primarily of 

 interwoven patches of tamarix, large sedges, coarse grasses, and a 

 species of bushlike woody perennial with purple flowers. All these 

 plant-types form rather discrete communities composed almost 

 exclusively of a single dominant type of plant. All voles were taken 

 the same night from the dense understory of the bushlike perennials. 

 Large series of Mus musculus and Gerbillus campestris and several 

 specimens of Crocidura russula Hermann were also obtained from this 



