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Dr. Cunningham— Surface Anatomy of the Primate Cerebrum. 223

of the operculum, the bottom of the underlying recess is the only fixed part
of this slit-like fissure. This is placed at some distance behind the parietooccipital
fissure as it cuts the upper border of the hemisphere (v. fig. 45),
and to avoid confusion I have applied to it the German term of " Affen-
spalte."

Fig. 46.—Cerebrum of Cebus albifrons as seen from above. Drawn by the American apparatus for
tracing orthogonal projections of the skull. The hinder end of the cerebrum was tilted
slightly upward, in order that the occipital region might be brought more fully into view.

/• •

. Sulcus frontalis inferior.

P* ■

. Ramus occipitalis.

p.c. .

Sulcus prsecentralis inferior.

s.t. .

. Corresponding furrow to the sulcus transr
.

. Fissure of Rolando.



versa occipitalis of Ecker.

s.

. Sylvian fissure.

p.o. .

. Parieto-occipital fissure.

p.

. Intraparietal sulcus.

a.n. .

. First annectant gyrus (arcus parieto-occipi-

p* .

. Sulcus postcentralis inferior.



talis.

p.* .

. Ramus horizontalis.

a.f. .

• " Affenspalte."

Pansch has aptly compared the occipital operculum of the apes to the
fronto-parietal operculum which covers the island of Reil. In this case we
may compare the bottom of the opercular recess, or " Affenspalte," to the
furrow which bounds the island of Reil above, and the superficial furrow
along the anterior edge of the occipital operculum with the posterior limb
of the Sylvian fissure.

But an operculum is not universally present in the apes. In four
hemispheres obtained from Cebus albifrons I find that the operculum is