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



Dimensions in inches. Ratio. 

 e. Greatest vertical depth of the fronto-parietal lobe 



{i.e. in a line cutting the postero-parietal gyrus) 2-4 0'68 



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

 ** Ditto diameter at the posterior ascending parietal 



lobes • . . 3-1 — 



/'. Length from the front of the middle lobe to hinder 



end of brain 2'5 0'52 



cj. Cerebral radius, occipital 2-4 0-7.3 



h. Ditto, frontal 3-0 0-70 



i. Ditto, temporo-parietal 2'6 0'G6 



/ 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 



m. Ditto, length 1-5 0-62 



n. Ditto, depth I'B 1-28 



Measurements of several parts of the brain idk.en from the preserved specimen, with 

 the ratios as in the preceding Table. 



Medulla oblongata. 



0. Greatest breadth 0-85 0.12 



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 0-65 0'72 



s. Width of ditto 0-4 0-80 



Optic thalamus. 



t. Length of the visible part I'l 0'84 



u. Width of ditto 0-4 0-80 



Pons Varolii. 



V. From the upper to the lower border . ..... 1'05 1-05 



to. 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 



