136 U.S. NATIONAL MUSEUM BULLETIN 2 75 



available habitats on the plateau and coastal plain ranging from the 

 exposed uplands with a scanty vegetative cover to the dense plant 

 cover of the larger wadis. They are perhaps most abundant in the 

 chaparral vegetation of the hillsides and throughout the dense vegeta- 

 tion of the coastal plain. They also occupy the rocky cliffs and talus 

 of the wadis and the rocky outcroppings along the coastal escarpments. 

 They were never collected from coastal dunes or other habitats com- 

 posed exclusively of sand. In these habitats they are supplanted by the 

 more sand-loving Gerbillus eatoni. 



The name brunnescens, meaning dark, dusky, or brown, alludes to 

 the brownish color of the dorsal pelage of members of this subspecies. 



Gerbillus campestris dodsoni (Thomas) 



Dipodillus dodsoni Thomas, Proc. Zool. Soc. London, vol. 2, pt. 1, p. 7, October 

 1902 (Ain Hammam, Tripolitania Province, Libya). 



Specimens examined. One hundred thirty-seven, from Cyr- 

 enaica: Tazerbo Oasis, 44; El Gezira (Tazerbo Oasis), 15; Bzema 

 Oasis, 9 (1 skin only); from Tripolitania: 5 km W Cussabat, 6; 



20 km N Gharian, 3; 20 km E Rumia, 2; 12 km S Chicla, 2; Ain 

 Hammam, 3 (BM); Gebel es Soda, 60 km S Socna, 4; from Fezzan: 

 Brach, 31; Temenhint, 2 (1 skull only); 75 km W Ubari, 2; 20 km 

 N Ghat, 1; Ghat, 1. 



Measurements. Averages and extremes of 17 adult males and 



21 adult females from Tazerbo Oasis, Cyrenaica Province, are, 

 respectively: Total length 223.1 (205-238), 222.9 (211-254); length 

 of tail 126.6 (118-140), 127.9 (111-148); length of hind foot 26.9 

 (25-29), 26.7 (25-28); length of ear 16 (15-17), 15.7 (14-17); oc- 

 cipitonasal length of skull 30.4 (28.6-31.7), 30.5 (28.7-32.1); length 

 of auditory bulla 9.7 (9.2-10.1), 9.7 (9.2-10.1); crown length of upper 

 molariform toothrow 3.9 (3.7-4.2), 4 (3.8-4.3); greatest breadth 

 across zygomatic arches 15.8 (14.6-16.5), 16 (15.1-16.5); least in- 

 terorbital breadth 5.5 (5-6), 5.4 (4.7-6); breadth of rostrum at level 

 of antorbital foramina 3.2 (3-3.4), 3.2 (3-3.4); length of nasals 

 11.9 (10.6-12.6), 11.4 (11-13). 



Diagnosis. Dorsal color ranging from Cinnamon-Brown, Sudan 

 Brown, and Verona Brown to Ochraceous-Tawny, all frequently 

 occurring in animals of the same local population; most specimens 

 with strong suffusions of darker hairs on dorsum, resulting in a varie- 

 gated or marbled appearance; other specimens uniformly colored; 

 in most specimens postauricular patches indistinct and suffused 

 with buffy hairs, and in others almost white; circumorbital areas 

 generally Light Buff with admixture of brownish hairs, in some 

 specimens darker and approaching color of dorsum; eye ring black; 

 scapular regions heavily suffused with brownish or buffy hairs, which 



