148 U.S. NATIONAL MUSEUM BULLETIN 2 75 



Diagnosis. Diminutive in size; pelage short and silky; upperparts 

 Buckthorn Brown, uniformly suffused with darker hairs and becoming 

 paler on sides and flanks; postauricular and supraorbital patches 

 distinct and white; subauricular areas with strong admixture of black 

 hairs; circumoral areas, portions of the cheeks, dorsal surfaces of 

 forelegs, hindlegs, feet, and entire underparts pure white; vibrissae 

 delicate and formed from both light and dark colored individual hairs ; 

 fore and hind feet extremely small, naked ventrally and each bearing 

 five digits with claws; tail Pinkish Buff, relatively long and with faint 

 terminal tuft, and appearing bicolored owing to moderate suffusions 

 of dark brown hairs dorsally; pinnae of ears extremely short and 

 sparsely haired ; outer surfaces of pinnae approaching color of dorsum ; 

 internal surfaces somewhat bicolored, becoming darker distally and 

 approaching Light Drab. Skull: Small and gracile; rostrum relatively 

 short ; zygomata fragile ; molarif orm teeth small and diverging slightly 

 anteriorly; braincase markedly expanded and appearing almost bul- 

 bous; auditory bullae noticeably large and markedly inflated ventrally; 

 basioccipital triangular-shaped posteriorly and projecting anteriorly 

 between auditory bullae as a narrow rod ; posterior lacerated foramina 

 large and distinct. 



Comparisons. Compared to a topotype of Gerbillus henleyi makrami 

 Setzer from Bir Kansisrob, Sudan Government Administrative Area, 

 Egypt, these specimens from Libya are larger in all respects and have 

 more prominently domed braincases. 



From topotypical Gerbillus henleyi mariae (Bonhote) from the vicinity 

 of Cairo, Egypt, these gerbils from Libya differ in having slightly 

 shorter skulls, smaller and less inflated auditory bullae, wider inter- 

 orbital breadths and rostra, shorter nasals, wider basioccipitals ante- 

 riorly, and smaller size of all external measurements except length of 

 ears. In color, G. h. mariae is noticeably darker with a greater suffusion 

 of grayish tones. 



These specimens from Libya are almost indistinguishable from 

 topotypes of G. h. henleyi from coastal Egypt but differ in slightly 

 larger size of body, interorbital breadth and width of rostrum, and 

 smaller occipitonasal length of skull. In overall size of body and occipi- 

 tonasal length they are nearer to G. h. mariae, but because they share 

 more characters with the nominate subspecies and have a range con- 

 tiguous with populations of the latter in western Egypt, they are here 

 referred to G. h. henleyi. 



Remarks. The diminutive size of members of this species serves to 

 distinguish them from all other gerbils in Libya. Until as recently as 

 1955, this distinctive species was unknown from Libya. Earlier col- 

 lectors in Libya tended to concentrate their efforts in the interior 

 oases and consequently neglected the coastal areas to which these 



