348 PHYSIOLOGICAL SERII>. 



Whales the distinction of exceeding the dimensions of t lu- 

 ll uinan bruin (Dubois, Bull. Soc. d'Anthropol. de Puris, 

 t. viii. 1897, p. 338). 



The cerebral hemisphere in each of the three Sirenians 

 consists of a great elliptical bladder, the lateral wall of 

 which is deeply indented at its mid-point. The hemisphere 

 of the Dugong is relatively much narrower and more like 

 those of the extinct Eotherium and Halitherium than that 

 of the Manatee. In this respect Rliytina occupies a position 

 intermediate between the two living genera. The olfactory 

 bulbs of Ilalicore are long, conical, projecting structures ; 

 those of Tricliechus are broad flattened cakes closely applied 

 to the anterior surface of the hemispheres ; and here again 

 Rhytina occupies the intermediate position. In all extinct 

 and living Sirenians the cerebellum has the same peculiar 



Brandt, Melanges Biolog., Bull, de 1'Acad. Imp. des Sci. 

 de St. Petersbourg, t. vi. 1867, p. 364. 



OKMSU CETACEA. 



Suborder ODONTOCETI. 

 Family DELPHINID^E. 



D. 511. The brain of a Porpoise (Phocana phoc cena). 



" The size of the brain differs much in the different genera of 



the Whole-tribe, and likewise in tin- different proportion it bears 



to the bulk of the animal. In the Porpoise, 1 believe, it i> 



t. and p<'rh;ips in th;il respect comes nearest to the Human. 



"The size of the cerebellum in proportion to that of the 

 cerebrum is smaller in the Human subject than in any animal 

 with which I am acquainted. In many quadrupeds, as the I 

 Cow, &c., the disproportion in si/e between cerebellum and 

 cerebrum is not great, and in this tribe it is still less, yet not NO 

 small as in the bird, &c. 



11 The whole brain in this tribe is compact, the anterior part of 

 the cerebrum not projecting so far forwards as in either the 



