MCKRITllEIilUM. 
105 
palate, and extend forwards in the specimen fignred in PI. VIII. as far as the front 
of 1. At their anterior end there is a pair of small posterior palatine foramina 
(not shown in the figure). The hinder edge of the ])alate is greatly thickened ; so 
also are the vertical plates, which, with the pterygoids, bound the mesopterygoid 
fossa. It seems possible that these bones helped to form the inner wall of the cavity 
in wliich the uncut germ of m.2) lies in the specimen figured in PI. VIII. The 
internal narial opening is about as deep as wide, and in its roof the vomer can be seen 
extending back to about the level of the hinder border of the palate. The 
are too much crushed and broken for description ; it appears that their thickened 
posterior angle w’as about opposite the anterior edge of the glenoid cavity. 
Several casts of the cranial cavity have been obtained. The best of these, taken 
from a skull (M. 8898) wdiich lacks most of the facial region, is figured (text-fig. 41). 
The brain is much larger in proportion to the bulk of the animal than is usually the 
case in the Eocene Mammalia, e. g. the Amblypoda ; and it is possible that the early 
tendency towards a considerable cerebral development shown in these primitive 
Proboscidea is one of the causes why the group has survived and flourished through 
so long a period. 
The olfactory lobes [o.l.) are large and pedunculate. They project forw^ards entirely 
in advance of the cerebral hemispheres, wTich are divided into anterior and posterior 
portions by a broad lateral groove (the pseudosylvian of Elliott Smith), wdiich runs 
dowmwmrds and forwmrds {p). The anterior (frontal) lobes {f.l.) are broad, rounded 
externally, and somewhat compressed from above downwards. The posterior 
(temporal) lobes {t.l.) project considerably beyond the frontal lobes both laterally and 
ventrally ; they are comparatively narrow from before backwards. Posteriorly the 
temporal lobes are separated (in the cast) from the cerebellum by a deep fossa. In 
the Mastodons and Elephants there is the same division of the hemisphere into 
anterior and posterior lobes by a deep depression (text-fig. 42), but in these later 
forms the temporal lobes have become greatly enlarged and project much more both 
ventrally and laterally, while the frontal portions of the hemispheres are more bent 
dowm and the olfactory lobes to a great extent lie beneath them. These changes seem 
to be correlated, at least in part, wdth the general shortening-up of the skull. 
The cerebellum [ch.) is comparatively small and narrow from before backwards ; it 
is entirely uncovered by the hemispheres. The ventral surface of the brain is not w'ell 
shown in the cast, but the position of the pituitary body and the bases of the fifth 
pair of nerves can be made out. 
A^arious other details of less importance can be observed, but these need not be 
referred to fully here, as I)r. Elliott Smith is preparing a memoir on this brain-cast. 
In the section relating to the Sirenia, some account will be given of the remarkable 
likeness betw^een the brain now described and that of Eosiren, another piece of 
evidence of the close relationship of the Sirenia wdth the Proboscidea. 
I’ 
