RODENTS OF LIBYA 243 



Diagnosis. Upperparts Cinnamon-Buff becoming darker on rump 

 owing to admixture of brownish hairs; rostral, mystacial, circum- 

 orbital, pectoral, and postauricular areas Light Buff; flanks and 

 lateral areas with slight admixture of brownish hairs; entire under- 

 pays, dorsum of front and hind feet and terminal portion of tail 

 white; pinna of ear sparsely furred and Clay Color; hind feet,ventrally, 

 heavily furred and frequently stained Pale Orange-Yellow; tail in- 

 distinctly bicolored, Pale Yellow-Orange dorsally and Light Buff 

 ventrally; pinnate tail sharply demarcated into a Bister anterior 

 portion and white posterior portion. Skull: Small; triangular in shape; 

 braincase prominently vaulted; zygomata convergent anteriorly; 

 auditory bullae moderately inflated; lachrymals relatively large; 

 rostrum narrow; zygomata relatively fragile; foramen on anterior 

 margin of angular process enlarged longitudinally; coronoid process 

 markedly reduced. 



Comparisons. When compared with topotypes of Jaculus jaculus 

 jaculus, J. j. whitchurchi differs in smaller body size, shorter tail, 

 shorter hind foot, markedly shorter ears, and generally smaller size 

 of cranium. Specimens of J. j. whitchurchi are paler and more uniformly 

 colored dorsally and have less suffusion of brown on the sides and 

 flanks. 



For comparisons with J. j. tripolitanicus , J. j. collinsi, and J. j. 

 arenaceous, see accounts of those subspecies. 



Remarks. This new subspecies of jerboa is largely restricted to 

 the Libyan littoral desert along the Gulf of Sirte. Specimens from 

 Giarabub, however, are referable to this subspecies and occur more 

 than 200 kilometers from the coast. Apparently, the vast hamada 

 north and east of the Sand Sea of Calanscio provides suitable habitat 

 for jerboas and allows for gene flow between these coastal and interior 

 populations. North and east of the Gulf of Sirte, dispersal is rendered 

 impossible by the escarpments of the Cyrenaican Plateau and Gebel 

 el Achdar. Widespread areas of sand between Gialo Oasis and the 

 coast also preclude interbreeding between J. j. whitchurchi and J. j. 

 collinsi. 



The type series was obtained from a complex of heavily vegetated 

 coastal dunes about one-half kilometer from the Mediterranean coast. 

 Specimens from Sirte and Marble Arch were collected from the 

 alkaline-clay soils of the coastal plain and farther removed from water. 



A specimen, 325802, from Giarabub, Cyrenaica, is markedly paler 

 and more uniformly colored dorsally than any other jerboa examined 

 from Libya. This particular specimen is an old female and probably 

 represents an extreme color variation incident to age. 



J. j. whitchurchi is proposed in recognition of Lt. Colonel Thomas 

 Whitchurch, former Commanding Officer of the 64th Engineering 



