585 
of Edinburgh^ Session 1865 - 66 . 
fissure of Sylvius, and excepting a small part of the most anterior 
gyrus, where it joined the inferior frontal, was completely con- 
cealed so long as the lips of the fissure were in situ. 
The brain A is the only specimen on the inner and tentorial sur- 
faces of the hemisphere of which I have been enabled to study the 
arrangement of the fissures and convolutions. The calloso-margi- 
nal sulcus (i ^) commenced anteriorly in front of the anterior end 
of the corpus callosum, and extended uninterruptedly backwards. 
When opposite the commencement of the posterior third of the 
corpus callosum it bifurcated, — one branch ascended and reached the 
margin of the great longitudinal fissure, the other ran backwards 
and joined the internal perpendicular fissure. From the calloso- 
marginal sulcus a few secondary fissures extended upwards and 
downwards into the marginal (17) and callosal (18) convolutions. 
The internal perpendicular (occipito-parietal) fissure (W), slightly 
convex forward, was continuous at the upper margin of the inner 
face with the external perpendicular fissure, whilst inferiorly, it 
joined the calcarine sulcus (I 1). Proceeding from its posterior lip, 
two connecting convolutions ran at once into the fissure ; one, (*) 
deeply placed, except at its origin, mounted upwards and outwards, 
and joined the deeper aspect of the postero-parietal lobule. Its 
concealed part exhibited an indication of subdivision into two gyri. 
The other, or inferior annectent gyrus (f) partly projected into the 
perpendicular, and partly into the calcarine fissure, and joined the 
lower portion of the quadrate lobule. The dentate sulcus (m m) 
was well-marked, and at its lower end was prolonged into the re 
curved part of the uncinate gyrus (19). The calcarine sulcus (I /), 
which possessed great depth, commenced posteriorly in a bifurcated 
extremity, the two limbs of the forks being almost equal in length. 
It extended forwards close to the dentate sulcus, but did not quite 
join it, so that the callosal (18) and uncinate (19) gyri were con- 
tinuous with each other in front of its anterior extremity. Within 
the calcarine sulcus two small gyri were found. One sprang from 
the floor of the fissure, and evidently corresponded to the calcarine 
gyrus, described by Mr Flower as so well developed in the brain of 
Gercopitliecus ; the other and larger arose from the internal occi- 
pital lobule (25) which formed the roof of the sulcus ; it projected 
towards the calcarine gyrus : anteriorly it became continuous with 
