RODENTS OF LIBYA 85 



Key to the Specie? of the Subgenus Gerbillus 



1. Skull prominently domed; anterior palatine foramina markedly enlarged. 



G. eatoni 

 Skull not prominently domed; anterior palatine foramina not markedly en- 

 larged 2 



2. Occipitonasal length of skull less than 30 mm; length of upper molariform 



toothrow less than 4 mm G. gerbillus 



Occipitonasal length of skull usually more than 30 mm; length of molari- 

 form toothrow usually more than 4 mm 3 



3. Tail with distinct brush; the latter never black G. pyramidum 



Tail without distinct brush; the latter frequently black G. aureus 



Gerbillus aureus Setzer 



Gerbillus pyramidum aureus Setzer, Proc. Biol. Soc. Wash., vol. 69, pp. 170-180, 

 Dec. 31, 1956 (12 km W Zliten, Tripolitania Province, Libya). 



General distribution of species. Libya; range probably also 

 includes coastal areas of Tunisia. 



Distribution in Libya. Coastal plain and littoral deserts of 

 northern Tripolitania. 



Distribution of the subspecies in Libya. 



Gerbillus aureus aureus. Tripolitania: Gebel Nefusa and the 

 coastal plain between Azizia and the Gulf of Sirte. 



Gerbillus aureus favillus. Tripolitania: Vicinity of Sirte; range 

 probably includes much of the coastal plain of the Gulf of Sirte. 



Gerbillus aureus nalutensis. Tripolitania: Coastal plain of extreme 

 northwestern Tripolitania . 



Comparisons. This species can be distinguished from Gerbillus 

 pyramidum, which it most closely resembles, by its markedly smaller 

 skull, smaller body, shorter, less tufted tail, generally darker color, 

 shorter and wider posterior palatine canals, wider anterior palatine 

 foramina, and longer molariform toothrows relative to occipitonasal 

 length. 



From Gerbillus gerbillus, G. aureus differs in larger body and skull, 

 larger molariform teeth, markedly less tufted tail, larger anterior 

 palatine foramina, more robust skull, heavier zygomata, and generally 

 darker, less orangish dorsal color. 



Gerbillus aureus can be readily separated from Gerbillus eatoni by 

 its larger body, larger and heavier skull, larger molariform teeth, 

 smaller anterior palatine foramina, longer posterior palatine canals, 

 smaller and less inflated auditory bullae, and markedly more flattened 

 braincase. 



Remarks. Setzer described Gerbillus pyramidum aureus ( = Gerbillus 

 aureus aureus) (1956, p. 179) and Gerbillus pyramidum favillus 

 (= Gerbillus aureus favillus) (1956, p. 180) as new subspecies of G. 

 pyramidum. In naming these new subspecies, he had only topotypical 



