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Dr. Cunningham—Surface Anatomy of the Primate Cerebrum. 225

intraparietal sulcus (c). This gyrus is sharply denned in front by a branch
of the intraparietal sulcus which extends upwards in front of it(/.). Posteriorly
it is limited by a furrow which corresponds with the upper part of
the bottom of the opercular slit (7.), whilst externally it is limited by the
short descending limb of the intraparietal fissure. The latter, however,
as in Cebus, has no connexion with the bottom of the recess formed by
the operculum.

Fourteen hemispheres obtained from Cynocephalus presented characters
which closely correspond with those represented in figure 47. Considerable
differences were noted in the degree of development of the first
annectant gyrus (A.). In all it was thrust deeply down below the surface,
but in some of the specimens (as, for example, the one which is figured
above), it was much more conspicuous than in the others.

In ten hemispheres taken from the macaque the condition present
was closely similar to that which we have described as existing in the
baboon.

An arrangement of the fissure, which is frequently present in the chimpanzee
(fig. 48, p. 226), leads us directly up to man. The first annectant
gyrus is still partially hidden from view, but it has risen much nearer to the
surface (/z.). It constitutes a distinct barrier to the communication between
the parieto-occipital fissure as it turns outwards on the hemisphere and the
intraparietal fissure. On removal of the operculum the descending short
limb of the intraparietal sulcus is seen to bound the first annectant gyrus
externally, and then bifurcate. The upper limb runs directly upwards,
and joining the bottom of the " Affenspalte," limits the first annectant gyrus
posteriorly (k.) whilst the lower limb turns downwards under cover of the
operculum, but is soon called to a halt, because the deep and hidden second
annectant gyrus interposes itself in the way. The upper terminal limb
is a new branch. We have seen in the baboon how a branch is sent up
from the intraparietal sulcus in front of the first annectant gyrus ; here in
the chimpanzee there is a branch which is sent up behind it, but this soon
loses itself in the bottom of the "Affenspalte." The lower terminal
branch of the bifurcation is simply the clown-turned end of the intraparietal
sulcus as we have seen it in Cebus and the baboon.

KOYAI IRISH ACADEMY.—CUNNINGHAM MEMOIRS, NO. VII. [29]