MOEEITHEEIUM. lOS' 



palate, and extend forwards in the specimen figured in PI. VIII. as far as the front 

 of m. 1. At their anterior end there is a pair of small posterior palatine foramina 

 (not shown in the figure). The hinder edge of the palate 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 which the uncut germ of m. 3 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 pterygoids 

 are too much crushed and broken for description ; it appears that their thickened 

 posterior angle was 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) which 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 forwards entirely 

 in advance of the cerebral hemispheres, which are divided into anterior and posterior 

 portions by a broad lateral groove (the pseudosylvian of Elliott Smith), which runs 

 downwards and forwards [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 

 down and the olfactory lobes to a great extent lie beneath them. These changes seem 

 to be correlated, at least in part, with 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 well 

 shown in the cast, but the position of the pituitary body and the bases of the fifth 

 pair of nerves can be made out. 



Various other details of less importance can be observed, but these need not be 

 referred to fully here, as Dr. 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 between the brain now described and that of Eosiren, another piece of 

 evidence of the close relationship of the Sirenia with the Proboscidea. 



p 



