1864.] MR. W. H. FLOWER ON THE BRAIN OF MYCETES. 337 
brain of the Primates, forms an important landmark upon the sur- 
face of the hemispheres, dividing it into two pretty nearly equal por- 
tions. It runs obliquely upwards and backwards, and is prolonged 
to the upper surface of the occipital lobe, extending to within *15!! 
of the middle line and °4! of the posterior end of the hemisphere. 
The antero-temporal fissure lies at the distance of +25" behind the 
Sylvian fissure, though approaching nearer at the upper end. It 
extends upwards only about two-thirds of the length of the Sylvian 
fissure. Behind the upper part of this, and parallel with it, is a 
straight sulcus about half an inch long, curving somewhat backwards 
at its upper end, placed near the limits of the temporal and occipital 
lobes. ‘This and an indentation on the edge of the hemisphere, at 
the great longitudinal fissure, three-quarters of an inch from the 
posterior end, more pronounced on the right than the left side, are 
the only indications of the external perpendicular fissure. Rather 
below the middle of the occipital lobe, on its outer side, is a short 
horizontal shallow sulcus, bifurcated in front on the left side, and 
represented on the right by a triradiate indentation. This completes 
the enumeration of the sulci on the outer face of the hemisphere 
behind the fissure of Sylvius. 
The fissure of Rolando is distinct, half an inch long, and quite 
transverse in direction. A quarter of an inch behind it, is a short 
transverse groove, and about the same distance in front a longitu- 
dinal one. On the frontal region is a strongly arched fissure, a little 
way above, but parallel to, the supraorbital border, slightly forked 
at its hinder or external end. The orbital surface of the hemisphere 
is marked by several irregular sulci. 
B. Sulci on the inner face of the hemisphere.—The calloso-mar- 
ginal sulcus is nearly straight ; it coincides in length with the corpus 
callosum, and bifurcates behind, its upper division not reaching the 
margin of the hemisphere. The calcarine fissure is quite simple, 
being joined by no other sulcus, and not bifureating at its posterior 
extremity. It is slightly curved, with the concavity downwards, and 
does not extend quite so far as the apex of the hemisphere. It is 
not so deep or complex internally as in most of the Old World Apes ; 
its internal relief in the ventricle, the hippocampus minor, is conse- 
quently small in proportion to the rest of the hemisphere. Above 
and nearly parallel to the last is a well-marked but shorter sulcus, 
. having a sigmoid curve. The dentate sulcus is continuous with the 
calcarine. The collateral is deep, short, and simple, curving at its 
lower part to the outer surface of the temporal lobe. Between its 
hinder extremity and the calcarine is a slight triradiate indentation. 
The brain just described, taken all together, presents certain cha- 
racters by which it is distinguished from that of all other Apes. 
The whole organ is small as compared with the size of the animal. 
The brain has in itself a contracted shrunken look, wanting that 
roundness and fulness seen in other genera, as Ateles and Cebus. 
Then the surface-markings are, considering the size of the brain, 
comparatively few and simple, and they depart remarkably from the 
ordinary type seen in the order. 
Proc, Zoou. Soc,—1864, No. XXII. 
