DE. J. MUEIE ON THE ANATOMY OF THE SEA-LION. 523 



retrovert obliquity, the upper end nestling in a fork beneath the lobule of the supra- 

 marginal convolution, which latter band-like gyrus forms its anterior lip. There 

 appears, moreover, to be an additional long straight sulcus derived from the upright 

 .Sylvian cleft. It strikes backwards and upwards, at an acute angle, starting about an 

 inch above the brain's base. The relations of this to the temporal sulci &c. I shall 

 presently have occasion to refer to, but take this occasion of mentioning that M. 

 Gratiolet 1 , in the Green Monkey, and Prof. Turner 2 , in the Chimpanzee, both record an 

 occasional backward offshoot from the primary Sylvian fissure. 



The latter anatomist has besides specially called attention, and given the name 

 intra-parietaP, to a sinuous fissure of considerable length, which forms a line of 

 demarcation betwixt the postparietal gyrus and the supramarginal with its lobule. 

 A sulcus corresponding to this, and bearing identical relations to the said convolutions, 

 can readily be traced in the brain of Otaria. It here springs just in front of the 

 anterior or supramarginal lip of the Sylvian fissure, quite at the sphenoparietal base. 

 Thence ascending laterally, it accompanies and bounds anteriorly and superiorly 

 the much inflected supramarginal gyrus, its lobule, and the angular gyrus towards the 

 upper temporal projection. Both in advance and to the rear of the lobule it exhibits 

 secondary spurred grooves ; one of these with a semilunar sweep cuts into the turn of the 

 ascending portion of the postparietal convolution. Posteriorly the intraparietal fissure 

 ceases at a bridge connecting the angular gyrus with the postparietal lobule; but 

 virtually it seems to go on to the supraoccipital region, in connexion with a sulcus 

 equivalent to an external perpendicular fissure. 



At its commencement below, on the lateral aspect of the sphenoparietal lobule, the 

 fissure of Rolando holds rather an indefinite position towards the intra- and antero- 

 parietal sulci ; but about halfway up its windings are more easily followed. It first 

 ascends perpendicularly, but in an /-shaped direction, to the fronto-parietal eminence. 

 Thence, wheeling backwards, it constitutes a longitudinal midhemispherical fissure. 

 The latter traverses the vertex to the occipital region; and what with an accessory 

 frontal furrow in communication with an antero-parietal fissure, that of Rolando may be 

 said to stretch the entire length of the summit hi a second lengthened /-shaped 

 manner, with subsidiary curt incisions. 



Though the representative of the antero-parietal fissure is better distinguished at its 

 spheno-orbital or subfrontal origin, yet as it mounts to the lateral and upper aspects 

 of the hemisphere its actual course is only recognized by snatches. It appears, how- 

 ever, by linear and stellate depressions, to wind round between the fronto-parietal areas, 

 somewhat beyond the middle and top of the hemisphere. 



Temporo-occipital fissures.— On its inferior or basal aspect the temporal lobe is 

 clearly furrowed by three main sulci. On its exterior these continue to run nearly 

 1 Mem. Plis cerebraux, p. 29. 2 P. E. S. Edinb. vol. v. 1866, p. 583. 



3 Turner, I. c. p. 581 ; Brain of Common Seal, /. c. vol. ii. p. 392.^ 



