RODENTS OF LIBYA 235 



foramina, longer and more widely flaring nasals, wider rostrum, 

 greater breadth of rostrum at level of antorbital foramina, and longer 

 molariform toothrow. In color, J. j. arenaceous differs from topotypes 

 of Jaculus jaculus jaculus in more uniform orangish dorsal coloration, 

 less suffusion of dark hairs on sides, darker pinna of ear, and vibrissae 

 of more uniform color. 



Compared to the type and type series of Jaculus jaculus whitchurchi, 

 J. j. arenaceous differs in greater overall length of skull and body, 

 smaller hind feet, less vaulted braincase, more robust zygomata, 

 larger, infraorbital foramina, larger foramen on anterior fossa of 

 angular process and larger size in all other cranial features. In color, 

 jerboas from Edri are darker, more variegated and far less uniformly 

 colored dorsally, have more admixture of dark hairs on the sides, and 

 have a more extensive buffy patch anterior to dark portion of pinna of 

 the tail. 



From the type and type series of Jaculus jaculus collinsi, J. j. 

 arenaceous can be differentiated by its more massive skull, relatively 

 narrower rostrum, larger lachrymals, slightly larger and more inflated 

 auditory bullae, more tenuous pterygoid processes, larger size of all 

 cranial measurements (except greatest breadth across zygomatic 

 processes and greatest breadth of braincase), and markedly larger hind 

 feet. Jerboas from Edri appear darker and more variegated in color 

 owing to greater suffusion of brownish hairs on dorsum, rump, and 

 sides. An old male, 322768, from Temenhint Oasis, 30 kilometers north- 

 east of Sebha, is markedly more orangish (ochraceous) in color of 

 dorsum and probably represents an aberrant specimen or an extreme 

 in pelage color incident to old age. 



This subspecies can be easily separated from J. j. sefrius Thomas 

 and Hinton from Ain Sefra, southwestern Algeria, by its significantly 

 smaller size of external and cranial measurements. 



A single specimen (BM, 12.11.14.53) of J. j. centralis Thomas and 

 Hinton from 85 kilometers south of El Golea, central Algerian Sahara, 

 somewhat resembles J. j. arenaceous in color, but in external measure- 

 ments and cranial characters it is much smaller. 



For comparisons with Jaculus jaculus tripolitanicus and Jaculus 

 jaculus cufrensis, see accounts of those subspecies. 



Remarks. Specimens from 2 kilometers southwest of Hun are the 

 only known representatives of J. j. arenaceous from Tripolitania 

 Province and are intergrades with J. j. whitchurchi. In length of upper 

 molariform toothrow, greatest breadth across zygomatic processes, 

 greatest breadth across antorbital processes, and length of the hind 

 foot they resemble the latter subspecies, but in the majority of cranial 

 and external measurements, they are closer to J. j. arenaceous to 

 which they are here referred. The vast hamadas to the north and east 



