336 DAVIDSON BLACK 
The whole course of the suprasylvian sulcus may be seen in a 
lateral view of the cast. In addition to the posterior horizontal 
limb common in ungulates, a long descending ramus of the supra- 
sylvian sulcus is to be noted. This sulcus is probably not homol- 
ogous with the postsylvian sulcus of carnivors, in which forms . 
this sulcus is only separated from the lateral group of sulci by a 
comparatively small area. 
The area ventral to the horizontal limb of the suprasylvian 
sulcus in the giraffe, as in the other ungulates, is of considerable 
extent, andis marked by two fairly constant sulci; the oblique 
suleus of Holl and the constellation termed by Kappers the tri- 
radiata posterior (l.c., p. 309). 
The pseudosylvian fossa is clearly indicated by a A-shaped, 
depressed area, the apical prolongation of which has been termed 
the processus acuminis. The caudal operculated lip of this 
fossa is notched by two or three slight compensating sulci and 
terminates in a well marked ramus posterior ectosylvii. 
Between the processus acuminis of the pseudosylvian fossa 
‘and the suprasylvian sulcus, a well marked arcuate fissure is 
situated. This constellation is present on both sides of the cast 
and is indeed one of the characteristic features of the giraffe 
brain. It will subsequently be shown that this arcuate con- 
stellation is of distinct diagnostic importance when present 
together with the form of ramus descendens suprasylyii here 
described. 
(b) Ocapia johnstoni (figures 4 to 6 and 20 to 22) 
This member of the family Giraffidae was first discovered 
in the Belgian Congo in 1899. No material other than the skin 
and skeleton has as yet been available for scientific study. The 
facts relating to the discovery of this animal, together with notes 
upon its mode of life and detailed descriptions of its skeletal 
parts, may be had in the memoirs of Ray Lankester and 
Fraipont (l.c.). 
In my preliminary report (1.c.) this animal was referred to as a 
‘hornless’ form, and indeed the description in Beddard’s text 
