Dr. J. E. Gray on the Genus Georychus. 389 



G. damarensis, and G. holosericeus is also much alike, but differs 

 from the fur of the other species in being shorter, rather more rigid, 

 apparently closer. 



The genus may be divided into four groups by the form of the 

 grinders, thus : — 



A. Grinders '^^. The crown of the upper and lower grinders nearly 



square, with a fold or groove on the inner and outer edges. 

 Georychus. (Fig. 1.) 



1. Georychus capensis. Gray, Cat. B.M. p. 148 ; see Water- 

 house, Ann. N. H. viii. t. 2. f. 2.' 



The perforation on the side of the skull in front of the orbit ob- 

 long, snbtrigoual, almost as wide as high ; forehead with a slight 

 wiug-like expansion over the front of the orbit ; the hinder wing of 

 the lower jaw longer than high, with a slightly rounded outline be- 

 neath. (Fig. 6.) 



Hab. Cape of Good Hope. 



2. Georychus albifrons, n. s. 



Fur ashy grey, with a large white spot on the forehead. 



Hab. E. Africa {Capt. Speke). 



This species is very like G. capensis, both in the colouring of the 

 fur and in the form of the grinders, but is not more than one-third 

 the size, and it has a large white spot on the forehead, and no white 

 on the cheeks. There is the same difference in the size of the skull ; 

 and the teeth are more worn, showing that it is as old. The brain- 

 box of the skull is much more ventricose. The teeth have a distinci: 

 fold on the inner side, but scarcely so on the outer ; but then they 

 are much worn. The expansion on the hinder part of the lower jaw 

 is nearly of the same form as that of G. capensis. 



Dr. Peters, in his ' Nat. Reise nach Mossambique,' t. 3.5. f. 3, gives 

 a figure of the top of what he believes to be a young specimen of 

 Bathgergus cacutiens. It is something like the skull of this spe- 

 cies ; but it may be the skull of the species to which Dr. Peters 

 refers it, for unfortunately the teeth, which would determine the 

 question, are not figured. 



B. Grinders |^. Crown of the front upper small, oblong, trans- 



verse, simple; of second, third, and fourth subtrigonal, with a 

 distinct fold or groove on the broader inner side ; the second 

 tooth the smallest: the first lower oblong, small; the second 

 square ; the third trigonal, the hinder side the smallest, with 

 a subtrifoliate crown. The hinder icing of the lower jaw broad, 

 nearly as high as wide, with a strongly arched outline below. 

 Heliophobivs, Peters. (Figs. 2 & 7.) 



3. Georychus pallidus. (Teeth, fig. 2 ; jaw, fig. ".) 

 Rufous grey ; side of face, chin, and beneath paler yellow-grey. 

 Hab. E'. Africa {Capt. Speke). 



