8 On South- African Rodents. 



taken at night with the aid of a lantern, to the light of which 

 it is attracted, when it may be struck with a whip or taken 

 in the hands. It might be mentioned that it is of the greatest 

 importance that the skull is not damaged, so death should be 

 caused by any other means than by a blow on the head. 



Malacothrix typicus, Smith. 



Otomys typicus, Smith (nee Cuvier), S. Afr. Quart. Journ. ii. 1834, 



p. 148. 

 Malacothrix typica, Wagn. Schreb. Saug., Suppl. iii. p. 498 (1843). 



This animal was made the type of his genus Otomys by 

 Dr. Smith, a genus which consisted of this species and 

 Otomys albicaudatus — Mystromys ; as stated above, the 

 generic name had already been used, which, under the 

 circumstances, may be considered rather fortunate. 



The genus Malacothrix is placed in the subfamily Dendro- 

 myinai, and this species is the only representative of the 

 genus. Specimens are extremely rare in museums. The 

 British Museum is indebted to Mr. A. Wolf Curry for a fine 

 series from Kimberley. 



Geoeychus, Illig. 

 (Prodi-. Syst. Mainm. et A v. p. 87, 1811.) 



Geoeychus, subgen. Geokychus, Gray. 

 (P. Z. S. 1864, p. 123.) 



This division includes only G. capensis, in which the 

 molars have deep infoldings of enamel on both outer and 

 inner surfaces, the fourth tooth or third molar only appearing 

 in extreme age. 



Geokychus, subgen. Ckyptomys, Gray. 



Georychvs, subgen. Cryptomys, Gray, t. c. p. 124. 

 Georychus, subgen. C'cetomys, id. t. c. p. 125. 



Includes all the other members of the genus, in which 

 the molars have only a vestige of an infolding of the enamel 

 on the outer surface of the molars in extreme youth and none 

 whatever even in early maturity, the fourth tooth or third 

 molar appearing at a very early age. 



I consider that these two forms are fully worthy of sub- 

 generic rank, though I do not follow all the divisions proposed 

 by Gray. 



