s 
338 DAVIDSON BLACK 
measures 67 mm., which is but little less than the corresponding 
distance in the giraffe. From the frontal to the occipital pole 
of the cerebrum, the maximum length is 106mm. The greatest 
interfloccular diameter is 55 mm. 
Brain stem, cerebellum and basis cranw. The appearance 
of the cerebellar portion of the cast is of interest for, in contrast 
to the giraffe, its configuration is such as to yield some accurate 
information concerning the morphology of the interfloccular 
mass. 
The two endocranial casts of this animal in my possession 
differ from each another considerably in the clearness with 
which the so-called vermis area is demarcated. Thus there is 
an individual variation in this region in the okapi. This, how- 
ever, may be accounted for readily -when the condition which 
obtains in this region of the skull among other ungulates is 
considered. 
Le Double (25, p. 45) has pointed out that the inner surface 
_of the skull in mammals in general is often moulded in its caudal 
part by the cerebellum to form three fossae: a median one for 
the lodgement of the median lobe (‘fossette cerebelleuse moy- 
enne’’), and two lateral ones for the lateral cerebellar lobes. 
This median fossa is present in many ungulates. In these forms 
this author further notes (p. 49) that caudally the falx cerebri 
may ossify at its junction with the tentorium and give rise to a 
projection, the inferior surface of which is concave and continu- 
ous with the median cerebellar fossa. This projection overlaps 
the vermis to such an extent among the Equidae that it has been 
described by Albrecht (1) as the ‘operculum of the vermis.’ 
Ossification of the tentorium, though common in adult Car- 
nivora, is rare in ungulates, especially in artiodactyles. In the 
latter group no indication of Albrecht’s operculum was observed 
in the skulls collected in the anatomical museum of this depart- 
ment except among the Cervidae, in which it was only indicated 
in the skulls of old animals (Cervus canadensis). 
From this it is reasonable to infer that the difference in the 
appearance of the vermis region in the two okapi casts in my 
possession is one due to age. 
