522 DE. J. MimiB ON THE ANATOMY OF THE SEA-LION. 



possess considerable vertical depth, and incline obliquely downwards, with an aspect 

 corresponding to that of the orbital plates. The parietal lobes are long from before 

 backwards, and broad from below upwards, or are of considerable height. The Sylvian 

 fissure gives them a sharp and deep line of demarcation behind and at their outer 

 margin ; but in front they blend with the frontal lobes. Each temporal lobe, as seen 

 on the base of the brain, has a long-elliptical form ; viewed laterally it appears shorter, 

 but of medium thickness. The occipital lobes sweep round the truncated posterior 

 hemispheres. Thus they have great proportional breadth, but, on the other hand, are 

 shallow from above downwards, the cerebellum occupying much of the vertically deep 

 occipital region. 



c. Clefts and sulci of Cerebrum, outer face. — In general pattern these and the gyri 

 offer agreement with what obtains in the Common Seal (Phoca vitulina) as depicted 

 by MM. Leuret and Gratiolet^ What may be considered distinctive between the 

 Otariadfe and Phocidfe I shall not stop to inquire. In the nomenclature I follow as 

 much as possible that applied to the human cerebiiim, with only incidental comment 

 on the counterpart of the smoother-brained Carnivora, e. g. Felidse. My descriptions 

 refer only to the right cerebral half of my specimen, unless where otherwise expressed. 

 With regard to the great longitudinal fissure or intercerebral cleft, it is of moderate 

 depth, the opposite lips approximating rather closely for the anterior half, but di- 

 varicating widely behind, thus exposing the vermiform process or middle lobe of the 

 cerebellum. On gently separating the central hemispheres the corpus callosum becomes 

 visible; but the corpora quadrigemina are hidden by the anterior rostrum of the 

 cerebellum (=incisura cerebelli anterior). 



Orbito-frontal fissures. — The inferior surface of the frontal lobe or supraorbital region 

 is grooved by three parallel longitudinal sulci, which trend slightly inwards anteriorly. 

 The outermost is shortest ; the innermost lodges the external root of the olfactory nerve. 

 On the upper and outer surface of the same lobe the sulci are more irregular. The 

 so-called crucial sulci of Carnivora^ are appreciable, though relatively neither long nor 

 deep. From each hemisphere they converge rearwards and together form a V-shaped 

 figure, placed quite at the fore extremities of the great marginal convolutions. The 

 presence of infero-frontal sulci is indicated by a couple of short transverse and oblique 

 indents, situate outside and above the supraorbital angle. Curved midorbital sulci are 

 better marked and in part continuous below and exteriorly with the antero-parietal 

 fissure. The supraorbital are broken, somewhat radiate grooves, located in proximity 

 and at right angles to the fore end of the great marginal gyri. 



Spheno-parietal fissures. — The well-defined Sylvian fissure forms a notable landmark 

 equally on the base and outer superficies. It ascends vertically or with only a slightly 



' Anat. Comp. Syst. Nerv. pi. 11. 



' Consult Leuret, "Phoca," 1. c. p. 392; Owen, "Cheetah," I. c; and Flower, " Proteles," P. Z. S. 1869, 

 p. 480. 



