THE EXTERNAL CHARACIEKS OF SCARTURUS. 659 



34. The External Characters of Sccn'turvs and other Jerboas^ 

 compared with those of Zapiis and Pedetes. By R. I. 

 PococK, F.R.S., F.Z.S. 



[Received May 9, 1922 : Read May 23, 1922.1 



(Text-figures 29-37.) 



Page 



Introduction , 659 



External Appearance 660 



The Rhinarium and Mouth 661 



Facial Vibrissffi 663 



The Ear 664 



The Fore Foot 667 



The Hind Foot 670 



Tails 674 



Anus and External Genitalia 675 



The Skull of Scarttirus 678 



The Genus Scirtopoda Brandt 679 



Conclusions 680 



Introduction. 



At the Scientific Meeting of the Zoological Society held on 

 May 24th of last year (P.Z.S. 192L p. 645), Major Flower ex- 

 hibited examples of three species of Egyptian Jei'boas (Jaculidie), 

 including a pair of the very rare four-toed form, Scarturus 

 tetradactylus, which had never been previously imported to 

 Europe alive, and was almost unknown in museums, apart from 

 the original example in Berlin, which was described as Dipus 

 tetradactylus by Lichtenstein in 1823. These examples were 

 exhibited in the Zoological Gardens for some months, but died 

 in the winter and came into my hands for examination *. To 

 compare with them I had several specimens of the two common 

 Egyptian Jerboas [Jactdtts jaculus and Scirtopoda orievtalis)^ ; 

 and also one of the five- toed genus Allactaga [A. indica), a pair 

 of examples of Zapus hudsonmmis or a. nearly related species, 

 and one male specimen of Pedetes caffei — the last-mentioned 

 examples having been preserved for many years in alcohol in the 

 Society's collection. The specimens above mentioned form the 

 material upon which this paper is principally based. 



* Although apparently fully adult when received, all the skeletal tissues at the 

 time of death were exceedingly frail. Even the tips of the incisor teeth were 

 uncalcified and pliable — a condition I never before observed in any mammal. 



t Good figures, drawn from life, and descriptions of these, as well as a brief 

 account of S. tetradactylus, may be found in Anderson and de Winton's ' Mammalia 

 of Egypt.' My reasons for adopting the name Scirtopoda are given below (p. 679). 



Proc. Zooh. Soc— 1922, No. XLY. 45 



