On the Squirrels hitherto referred to Paraxerus. 33 



IV. — On the Striped Squirrels hitliprto referred to the 

 Genus Paraxerus. By Oldfielu Thomas. 



(Published by permission of the Trustees of the British Museum.) 



The genus Paraxerus, as restricted in my paper on the 

 genera of African Sciuridas*, contains two superficially 

 distinct sets of species — those of uniform colour, or, at most, 

 with an indistinct whitish line down each side of the back, 

 and those with fourf conspicuous black bands down the 

 dorsal area with white or yellowish lines between them. 



In connection with an examination of some striped squirrels 

 brought by Major Christy from the Bahr-el-Ghazal, I have 

 again studied the skulls of the members of these two groups, 

 and find that there are certain cranial and dental characters 

 by which they can in all cases be distinguished from each 

 other. It would, therefore, appear convenient that groups so 

 conspicuously different externally should be separated generi- 

 cally. The unstriped species will therefore bear the name of 

 Paraxerus, with P. cepapi as genotype, while those that are 

 striped may form the following new genus : — 



Tamiscus, gen. no v. 



Dorsal surface conspicuously black-striped. 



Skull on the whole as in Paraxerus, with similar short 

 muzzle. Anteorbital foramen forming a high narrow slit, 

 that of Paraxerus more subtriano-ular, broader at base. 



it i 



Teeth. Incisors generally thrown more forwards, those of 

 Paraxerus forming an angle with the tooth-row of about 80° 

 (75° to 85°), while those of Tamiscus are usually about 90° 

 more or less, attaining 100° in the type of T. vulcanorum. 

 The terminal wearing-edge notched, very much as in Mus. 

 those of Paraxerus being quite normal, as in Rattus. 



Molars less hypsodont, the crowns more abruptly marked 

 off from the roots. Looking at these teeth from the inner 

 side, the large internal root is narrow, well-spaced from its 

 neighbours on each side, and abruptly broadens out. above at 

 the crown. In Paraxerus, on the other hand, this root is 

 proportionally larger below, so as more nearly to approach its 

 neighbours, and quite gradually broadens upwards to the 

 crown. Owing to the greater size of the roots in Paraxerus, 

 their tips are more generally visible on the upper side of the 

 maxillary than in Tamiscus. 



Genotype. Tamiscus emini (Sciurus emini, Stuhlin.). 



* Ann. & Mag. Nat. Hist. (8) iii. p. 467 (1909). 

 t Two only in alexamlri. 



Ann. cD Mag. N. Hist. Ser. 9. Vol. i. 3 



