848 



ON THE RODENT GENUS HETEROCEPHALUS. [NoV. 17, 



similar ; but the lower jaw of the type of that species has unfortunately 

 been lost. 



The incisors, as in the aUied genera, project nearly horizontally 

 forward ; and their anterior faces are somewhat flattened and bevelled 

 on their interior halves, so that, as they wear down, the resulting edge 

 of the two incisors combined is more or less W-shaped, but with 

 the outer arms of the W very much shorter than the inner. 



Externally I can find no specific difi'erences whatever, except iu 

 the greater size of the hind feet of H. glaber. It must, however, 

 be remembered that in such a genus as Heterocephalus, iu which 

 there are neither ear-conchs, to vary in shape and size, nor hairs, 

 to vary in colour and length, and where there is only one possible 

 manner of life, there is very little room for the ordinary forms of 

 specific variation as found in other genera of mammals. 



The measurements of the type specimens of the two species are as 

 follows : — 



Head and body . . 



Tail 



Hind foot 



Forearm and hand 



Head 



Muzzle to ear . . 

 Muzzle to eye . . 

 Eye to ear 



H. pkillipsi 

 ( 2 in spirit), 

 mm, 



80 



35 



16-6 



21-0 



21-5 



15-2 



7-0 



7-0 



H. glaher 

 (stuffed). 



mm . 



(c) 95 

 39 

 21-2 



(c) 20-0 



Skulls ; 



H. phillipd. H, glaber. 



Occiput to tip of nasals 16"1 21*5 



Occiput to tip of incisors 19*4 26'4 



Basal length' 16-0 21-5 



Greatest breadth 13-6 18-3 



Brain-case, length 9*2 II -0 



Brain-case, breadth 9"4 12*0 



Nasals, length 5-1 7-8 



Nasals, breadth 3*2 4*4 



luterorbital breadth 5*1 6*0 



Back of incisors to m' 5v 8'0 



Palatine foramina 1*1 2*3 



Palatine foramina to posterior nares 4'0 6'1 



Basi-cranial axis 6* 1 — 



Palate, length 9-1 13-6 



Palate, breadth outside m' 4'3 5'0 



Palate, breadth inside m^ 1*5 2*2 



Palate, least breadth inside molars . 1*2 TS 



Incisors, breadth 2*1 2".9 



Incisors, length 3*9 5*4! 



^ From basion 



