340 DAVIDSON BLACK 
and suprasylvian sulci, together with the diagonal, are worthy 
of note. In the okapi, as is usually the case in the Cervidae and 
often in other ungulates, the ansate sulcus joins the coronal to 
the suprasylvian. 
The suprasylvian is also continuous with the diagonal on the 
right side (fig. 6), though this is not the case on the left. 
The continuity of the suprasylvian and the diagonal sulci is a 
common phenomenon among ungulates, appearing in both the 
Perisodactyla and Artiodactyla (figs. 10 to 16) and also among 
carnivors (11). This is regarded by Kappers as evidence that 
the diagonal sulcus is originally an anterior branch of the supra- 
sylvian. 
Thus the continuity of the suprasylvian and diagonal, which 
occurs on the right side, and the junction of the coronal and 
suprasylvian by the ansate, which occurs on both sides, repre- 
‘sent, in the okapi, generalized ungulate characteristics which 
have been retained. 
Laterally, the posterior rhinal fissure and the pyriform area 
lying below it may be clearly seen, but the anterior rhinal fissure 
cannot be definitely distinguished. 
The pseudosylvian fossa is represented on the surface by a 
short vertical fissure and, as the frontal operculum is well de- 
veloped, only a very small part of the anterior ectosylvian sul- 
cus is visible. 
The presylvian sulcus is large and extends frontad till it almost 
reaches the coronal, from which it is only separated by a narrow 
space. 
The broad area between the short processus acuminis of the 
pseudosylvian fossa and the quite dorsally placed suprasylvian 
sulcus, is marked by a well developed arcuate constellation. 
The descending ramus of the suprasylvian sulcus is well 
developed and differs from the sulcus bearing this name in the 
giraffe by being more caudally placed and by cutting the rhinal 
fissure. This communication with the rhinal fissure is apparently 
brought about by a junction of the descending ramus with the 
upturned ramus posterior ectosylvil, behind the caudal pseu- 
dosylvian operculum. 
