RODENTS OF LIBYA 119 



patches distinct and pure white; pinna of ear same color as dorsum, 

 sparsely haired and with row of buffy hairs along anterior margin; 

 vibrissae composed of nearly equal numbers of brown and white hairs; 

 dorsal and ventral surfaces of fore and hind feet white, densely haired 

 and each bearing five digits with claws; tail indistinctly bicolored, 

 Pinkish Buff dorsally and Pale Pinkish Buff ventrally, and terminating 

 in a conspicuous brownish-colored pencil; entire underparts white. 

 Skull: Relatively small; rostrum wide; molariform teeth relatively 

 large; anterior palatine foramina markedly narrow and slitlike; 

 auditory bullae rather bulbous. 



Comparisons. From Gerbillus pyramidum pyramidum as known from 

 several localities in Giza Province, Egypt, Gerbillus pyramidum 

 hamadensis differs in markedly smaller size of body and skull, relatively 

 smaller and more slitlike anterior palatine foramina, less ventrally 

 inflated auditory bullae, less robust zygomata, and smaller lachrymals. 

 This subspecies is much paler and uniform in dorsal color and has 

 more prominent postauricular patches and lighter colored pencil. 



Compared with topotypes of Gerbillus pyramidum tarabuli, G. p. 

 hamadensis is noticeably smaller in all cranial and external characters, 

 being of comparable size only in crown length of molariform toothrows 

 and breadth of rostrum. In color, members of this new subspecies are 

 slightly paler, have a grayer cast owing to a greater suffusion of 

 grayish hairs on dorsum, and have a pencil of a slightly lighter color. 



These gerbils can be readily distinguished from representatives of 

 Gerbillus pyramidum hirtipes Lataste from Ain Sefra, southwestern 

 Algeria, by paler dorsal color, longer and more thickly tufted tails, 

 larger auditory bullae and molariform toothrows, and generally larger 

 size of all other measurable cranial characters. 



In general body size and length of hind foot and ear, G. p. hamadensis 

 resembles Gerbillus aureus nalutensis but differs markedly in having 

 smaller anterior palatine foramina, longer posterior palatine canals, 

 more robust zygomata, larger molariform teeth, longer and more 

 tufted tail, paler and less varied dorsal color with less suffusion of 

 black on rump, and larger size of all cranial measurements. 



Remarks. Members of this subspecies can be distinguished from all 

 others in Libya by their conspicuously smaller size and paler dorsal 

 color. Throughout the range of this subspecies, animals vary locally. 

 Gerbils from 5 kilometers south of Socna, Tripolitania Province, are 

 more strongly suffused with brown on the back and dorsum of tail, 

 have slightly darker pencils, slightly longer and wider anterior palatine 

 foramina, more gracile skulls, less prominent supraorbital ridges, and 

 are slightly smaller in all cranial measurements. Two specimens, 

 322097 and 322098, from 30 kilometers south of Bu Ngem, Tripolitania 

 Province, have slightly smaller anterior palatine foramina, but, in 



