DE. J. MUEIE ON THE ANATOMY OF THE SEA-LION. 525 



and forms a curved lobule, which joins that of the antero-parietal at the internal perpen- 

 dicular fissure. It, moreover, is in continuity with the extremity of the angular gyrus. 



The third ascending parietal appears as a band sunk within the Sylvian fissure, and 

 constitutes the anterior lip of the latter, or becomes what in man has been termed 

 supramarginal. Its upper loop embraces the top of the upright Sylvian fissure, a 

 descending wedge-shaped turn serving as a division between the latter sulcus and its 

 long posterior branch. The continuation of the supramarginal gyrus and lobule is 

 equivalent to the angular convolution, which bounded above by the intraparietal 

 fissure, below by the 2nd Sylvian parallel fissure and temporal lobes, strikes obliquely 

 upwards to the summit of the occipital region. A lobular expansion is manifest 

 outside that of the postparietal, a narrow bridge connecting these, and another joining 

 it to the posttemporal convolution.. 



Temporal and occipital gyri. — The anterotemporal is an inversely U-shaped fold. 

 Its short upper limb sinks into the middle of the Sylvian fissure ; the longer lower limb 

 curves forwards below the lobe, and partly bounds the Sylvian cleft behind. The middle 

 temporal gyrus is a single sinuous S-shaped fold which above abruptly ends or dips into 

 the post-Sylvian fissure. The posttemporal convolution goes parallel to the latter as 

 far as the post-Sylvian sulcus, meantime exhibiting greater tortuosity. Above the mid- 

 temporal it doubles or is transformed into a lobule which stretches up to the supra- 

 occipital region and is there connected with the occipital gyri. As above mentioned, a 

 narrow bridge unites the posttemporal to the angular gyrus, and breaks the upward 

 continuity of the post-Sylvian fissure. 



An infraoccipital gyrus of a simple band-like character is well marked behind the 

 posttemporal. Mid- and supraoccipital convolutions are less easily defined, or are 

 represented by those post upper and inner strips which overhang the cerebellum and 

 outwardly blend with the lobular terminations of the posttemporal and angular gyri. 



e. Sulci and Gyri of the inner face. — The great marginal convolution extends to 

 about opposite the middle of the corpus callosum, has but moderate depth, and is 

 broken into several lozenge-shaped folds by short secondary sulci. The calloso-marginal 

 fissure is interrupted thrice by upward intrusive folds ; nevertheless it can be followed 

 to nearly above the splenium. The convolution of the corpus callosum presents a 

 lower straightish plication and upper diverticula. A posterior downward loop rounds 

 the corpus callosum, forming a callosal lobule in proximity to the upward fold of the 

 uncinate gyrus. A second loop above and in front of that mentioned reaches forwards 

 and lies subjacent to a third and horizontal loop, representative of a quadrilateral 

 lobule. This is bounded behind by a somewhat forward, shelving, internal, per- 

 pendicular fissure, which dips into a fold or ridge leading to the relatively large internal 

 occipital lobule. The latter lobule has a rounded exterior border approaching close to 

 the occipital edge, a marginal occipital sulcus intervening, which sulcus has com- 

 munication in front with the internal perpendicular fissure. Inferiorly the internal 



vol, viii. — part ix. June, 1S74. 4d 



