486 PROCEEDINGS OF THE NATIONAL MUSEUM vol. loe 



or nearly equal to the latter. The skull is, in general, smaller, the 

 cheekteeth are decidedly smaller, and tJie auditory bullae are markedly 

 larger. The pterygoid fossae are less open and the anterior palatine 

 foramina are shorter. In many respects principulus is like watersi 

 and may eventually prove to be onlj' a subspecies of that form. 



GerbiUus (Dipodilhis) stigmonyx stigmonyx (Heugliii) 



Figure 4,d 



Merioncs stigmonyx Heuglin, Reise in Nordost-Afrika, vol. 2, p. 78, 1877. 



(Khartoum.) 

 GerbiUus stigmonyx Infeolus Thomas, Ann. Mag. Nat. Hist., ser. 7, vol. 8, p. 275, 



October 1901. (Duem.) 



Specimens Examined: Seven, all in BM, from: Duem, 1; Khar- 

 toum, 5; El Kowa, 1. 



Measurements: An adult female from El Kowa has the following 

 external measurements: Length of head and body 87; length of tail 

 104; length of hind foot 20. An adult male from Khartoum and the 

 adult female above have, respectively, the follomng cranial measure- 

 ments: Greatest length of skull 27.3, 26.5; condyloincisive length 

 24.8, 23.6; length of anterior palatine foramina 4.9, 4.7; crow^n length 

 of upper toothrow 3.7, 3.8; length of auditory bullae 9.4, 9.4; least 

 interorbital width 4.9, 4.9; length of nasals 9.9, 9.8; width of rostrum 

 at level of antorbital foramen 2.9, 2.7; greatest width across zygomatic 

 arches 14.2, 14.2; breadth of braincase 13.5, 13.6. 



Remarks; GerbiUus s. stigmonyx, when compared to G. mackil- 

 ligini, shows a somewhat longer head and body and a shorter tail. 

 The color is markedly lighter and the heavy brush on the tail found 

 in the latter is not at all pronounced in the former. The skull is 

 narrower at the back, the auditory bullae are markedly less inflated, 

 the anterior palatine foramina are more open and somewhat shorter, 

 the molars are heavier, and the pterj'-goid fossae are more open. The 

 rostrum is decidedly heavier in stigmonyx and the infraorbital foramen 

 is more open. 



The type of luteolus differs neither in pelage characters nor cranially 

 from any of the specimens from Khartoum, and, assuming the speci- 

 mens from Khartoum to be topotypes of G. stigmonyx, the name G. 

 s. luteolus described by Thomas from Duem must fall as a synonym. 



GerbiUus (Dipodillus) watersi Dc Winton 



GerbiUus (DipodiUus) watersi De Winton, Nov. Zool., vol. 8, p. 399, December 

 1901. (Shendy, Upper Nile.) 



Specimens Examined: Fort3^-two, all in BM, from: Shendy, 5; 

 Kerma, 2; Shcreik, 1; Atbara, 2; Merowe, 7; Khartoum, 10;|Abu 



