RODENTS OF LIBYA 109 



Gerbillus gerbillus gerbillus (Olivier) 



Dipus gerbillus Olivier, Bull. Sci. Soc. Philom., Paris, vol. 2, p. 121, 1801 (Giza 

 Province, Egypt). 



Specimens examined. Twenty-six, from Cyrenaica: Giarabub, 10 

 (1 skin only); Bahr el Tubat, 21 km ESE Giarabub, 11; 24 km SSE 

 Giarabub, 5. 



Measurements. Averages and extremes of five males and measure- 

 ments of two females from Giarabub are, respectively: Total length 

 214 (205-221), 214, 205; length of tail 127 (121-135), 122, 119; length 

 of hind foot 29 (28-30), 31, 32; length of ear 13 (13-13), 12, 13; occip- 

 itonasal length of skull 28.7 (28.1-29.4), 28.1, 27; length of auditory 

 bulla 10.7 (10.2-11.2), 9.9, 10.2; crown length of molariform toothrow 

 3.7 (3.6-3.8), 3.4, 3.6; greatest breadth across zygomatic arches 15.3 

 (14.5-15.8), 14.7, 14.9; least interorbital breadth 5.9 (5.7-6), 5.6, 5.5; 

 breadth of rostrum at level of antorbital foramina 3 (3-3.1), 3, 2.8; 

 greatest length of nasals 10.6 (9.9-11.6), 10.6, 10.4. 



Diagnosis. Upperparts Cinnamon-Buff becoming paler on sides 

 and flanks owing to suffusion of whitish hairs; circumorbital regions, 

 mystacial and pectoral areas, dorsal surfaces of fore and hind feet, and 

 entire underparts white; postauricular patch distinct and white; 

 vibrissae short and composed of brownish and white hairs; pinna of 

 ear almost naked, Warm Buff, and with row of fine, buffy hairs on 

 anterior margin; fore and hind feet sparsely haired ventrally and 

 bearing five digits, each with a claw; tail indistinctly bicolored Light 

 Ochraceous-Buff above and Light Buff below, and with a prominent 

 terminal pencil, Tilleul-Buff dorsally and Pale Pinkish Buff ventrally. 

 Skull: Medium in size and moderately robust; zygomata heavy; 

 lachrymals large; molariform teeth moderately large; auditory bullae 

 markedly large and inflated; braincase moderately domed. 



Comparisons. From topotypical Gerbillus gerbillus gerbillus from 

 Alexandria Road, 5 miles northwest of the Pyramids of Giza, Cairo 

 Area, Egypt, specimens from Giarabub and vicinity differ in having 

 slightly heavier zygomata, larger lachrymals, larger and more in- 

 flated auditory bullae, slightly larger molariform teeth, slightly 

 narrower basioccipitals and shorter overall size of body. In color, the 

 majority of specimens are closer to Gerbillus gerbillus psammophilous, 

 whose range is farther west and south. In the majority of cranial 

 characters and in external measurements, however, they resemble 

 the nominate subspecies to which they are here referred. 



For comparisons with Gerbillus gerbillus aeruginosas and G. g. 

 psammophilous, see accounts of those subspecies. 



Remarks. In cranial characters, these specimens from Giarabub 

 are indistinguishable from those from Bahr el Tubat and Siwa Oasis, 

 western Egypt. These populations also do not differ significantly 



