RODENTS OF LIBYA 91 



supraorbital patches white; mystacial, rostral, circumoral, and 

 pectoral areas white, the latter tinged with buff; vibrissae short and 

 with numerous dark hairs; pinna of ear drab-colored distally, basally 

 approaching color of dorsum and with row of buffy hairs on anterior 

 margin; fore and hind feet densely haired, white, and with five digits 

 bearing claws; entire underparts pure white; tail Cinnamon-Buff with 

 admixture of brownish hairs dorsally, grading to Pinkish Buff ventrally 

 and terminating in a distinct blackish-brown pencil. Skull: Relatively 

 large and robust, auditory bullae large and bulbous; molariform 

 toothrows long, individual teeth large; rostrum wide; braincase wide 

 and flat. 



Measurements. Averages and extremes of 17 adult males and 

 13 adult females from the type locality, with the measurements of 

 the type in brackets, are, respectively: Total length 231.2 (21S-249), 

 224 (213-238), [234]; length of tail 130.4 (117-142), 125.6 (106-132), 

 [130]; length of hind foot 29.2 (27-31), 28. S (27-31), [30]; length of 

 ear 14.9 (14-16), 14.3 (13-15), [15]; occipitonasal length of skull 30.3 

 (29.1-31.5), 29.5 (28.7-30.3), [30.7]; length of auditory bulla 11.1 

 (10.5-11.5), 10.9 (10.2-11.4), [11.3]; crown length of upper molariform 

 toothrow 4.3 (3.9-4.5), 4.3 (3.9-4.4), [4.5]; greatest breadth across 

 zygomatic arches 16.2 (15.7-17.1), 15.6 (15.1-16.1), [16.3]; least 

 interorbital breadth 5.9 (5.3-6.3), 5.8 (5.5-6.1), [6]; breadth of 

 rostrum at level of antorbital foramina 3.3 (2.9-3.4), 3.1 (3-3.4), 

 [3.4]; greatest length of nasals 11.6 (11.1-12.2), 11.3 (10.6-11.6), 

 [11.8]. 



Comparisons. From topotypes of Gerbillus aureus aureus, the 

 type and paratypes of G. a. nalutensis differ in having more robust 

 skulls, markedly larger and wider auditory bullae, markedly longer 

 molariform toothrows, larger individual molariform teeth, wider 

 braincases, and wider and shorter rostra. In color, G. a. nalutensis is 

 somewhat darker dorsally with more suffusion of black hairs on the 

 rump, and the tail has a darker colored pencil. 



This new subspecies can be distinguished from Gerbillus aureus 

 favillus by darker dorsal color, darker (almost black) pencil, markedly 

 longer molariform toothrows, larger size of individual teeth, much 

 larger, more bulbous auditory bullae, more domed braincase, wider 

 rostrum, and markedly larger size of body and cranium. 



Remarks. Although a fundamental morphological pattern is 

 always present in members of this subspecies, they vary considerably 

 in color and cranial characters. As in the other two subspecies of 

 G. aureus, dorsal color ranges from the typical dark form, with a 

 heavy suffusion of black, to the more uniformly colored "golden" 

 form. Specimens showing all gradations in intermediate color are also 

 known. Cranially, this subspecies is remarkably polymorphic, partic- 



