DR. J. MUEIE ON THE ANATOMY OF THE SEA-LION. -521 



Dimensions in inches. Ratio. 



e. Greatest vertical depth of the frontoparietal lobe 



(i.e. in a line cutting the postero-parietal gyrus) 2*4 068 



* Ditto diameter at the frontal lobes (the point) . . 2"4 — 

 ** Ditto diameter at the posterior ascending parietal 



lobes " 3T — 



f. Length from the front of the middle lobe to hinder 



end of brain 2-5 0-52 



</. Cerebral radius, occipital 2'4 - 73 



h. Ditto, frontal 3-0 (HO 



i. Ditto, temporo-parietal 2 - 6 0*66 



j. Ditto, vertical 2-6 0-56 



k. Projection of the cerebrum beyond the cerebellum does not obtain. 



Cerebellum. 



I. The greatest breadth 3 9 1-08 



to. Ditto, length 1*5 062 



n. Ditto, depth 1-8 1-28 



Measurements of several parts of the brain taken from the preserved specimen, with 

 the ratios as in the preceding Table. 



Medulla oblongata, 



o. Greatest breadth 0-85 0.12 



4 



Corpus callosum. 



p. Length (in a straight line) 1*5 0*48 



q. Average thickness 0*17 0*39 



Corpus striatum. 



r. Length of the visible part - 65 0*72 



s. Width of ditto 0-4 0-80 



Optic thalamus. 



t. Length of the visible part IT 0-84 



u. Width of ditto 0-4 0-80 



Pons Varolii. 



v. From the upper to the lower border 1*05 T05 



w. Thickness 0-8 0-50 



b. The Cerebral Lobes. — Of the five lobes of the cerebrum which most modern 



anatomists recognize in the mammalian brain generally, four are tolerably well defined 

 in Otaria — the fifth or central lobe being much less so, if at all distinct. The 

 frontal lobes are short, but of moderate breadth and height; their orbital surfaces 



