THE BRAIN OF THE SUMATRAN RHINOCEROS. 145 
a continuous oblique line, fairly regularly bent upon itself, first one 
way and then the reverse. 
The median oblique gyrus is divided into two nearly equal moieties 
by a fissure running parallel to its direction, each half being much - 
doubled upon itself. Anteriorly bridging minor convolutions blend it 
with the internal oblique gyrus, about one third distant from the ante- 
rior extremity of the hemisphere, in front of which the broad oblong 
cerebral surface is divided by a longitudinal suleus into two equal 
moieties, both convoluted. In the great breadth and division of this 
anterior portion the Rhinoceros under consideration differs from the 
Equide, and agrees with Rhinoceros wnicornis. 
The external oblique gyrus is much doubled on itself, and sepa- 
rated from the Sylvian fissure, which it surrounds, by minor convolu- 
tions, more strongly differentiated anteriorly. 
On the inner surface of the hemisphere the hippocampal gyrus is 
seen to be traversed by minor sulci and slight folds which ran parallel 
to its length, as in the Equide, the eaJloso-marginal sulcus following 
the anterior bending of the corpus callosum, and not, as in so many 
Artiodactyla (but not in the Equidew), becoming superficial ante- 
riorly. ‘ 
The fissure of Sylvius forms an open angle, at the bottom of which Page 413. 
are situated a number of small convolutions radiating from a point, 
which I take to be the island of Reil. 
The under surface of the brain exhibits the smooth surfaces of the 
middle lobes of the hemispheres and the smooth broad roots of the 
equally broad olfactory nerves, which are not lobate at their anterior 
extremities. The optic chiasma is short, the two optic nerves springing 
from its anterior surface quite close together. The pons Varolii is not 
large, the reverse being the case with the crura cerebri and the 
corpora albicantia. 
The lateral lobes of the cerebellum are small compared with the 
median portion, as is the case in the Ungulata generally. 
DESCRIPTION OF PLATE 4 (LXX), 
Brain of Ceratorhinus sumatrensis. 
a 
Fig. 1. Lateral view of right cerebral hemisphere. 
2. Inferior view of left half of brain. 
3. Superior view of left half of brain. 
4. Internal view of right cerebral hemisphere. 
rer 
