202 



TEETIART VERTEBEATA OP THE EAYtTM. 



(frontal) portion {f-l.) and a lateral (temporal) prominence {t.l.) by a well-marked 

 depression, which seems to be homologous with the " pseudosylvian " * depression (p.) 

 in the brains of recent Sirenians and Proboscidea. The cerebellum [ch.) is small, but 

 its limits are not well shown in the cast. The base of the brain also is not well 

 preserved, only the roots of one pair of nerves, probably the fifth, being shown. 



B. 



Cast of the cranial cavity of Eosiren Uhyca : A, from above ; B, from right side. 

 cb., cerebellum ; f.l., frontal lobes ; 61., olfactory lobes ; p., pseudosylvian depression ; t.l., temporal lobes. 



|- nat. size. 



In Eotherium the general form of the brain is not unlike that figured, but the 

 pseudosylvian depression is very slightly marked, so that the separation of the hemi- 

 spheres into anterior and lateral lobes is obscure. The chief interest of the brain of 

 Eosiren lies in its remarkable similarity with that of Moeritherium {cf. text-fig. 41, 

 p. 106). In both animals the hemispheres are divided in a quite similar way by the 

 pseudosylvian depression, and the cerebellum is relatively small. In Mceritherium, as 



* Elliot Smith, 'Catalogue of the Physiological Series, Museum, Coll. Surgeons,' vol. ii. ed. 2 (1902) 

 p. 344. 



