THE BRAIN IN MARSUPIAL ANIMALS. 
95 
The same letters indicate the same parts in each figure. 
A. Cerebral hemispheres. 
B. Optic lobes, or corpora quadrigemina. 
C. Cerebellum. 
* Place between the vermiform process and lateral lobes, where the medul- 
lary matter of the cerebellum is superficial. 
a. Olfactory lobes or ganglions. 
b. Pons Varolii, or cerebellic commissure. 
c. Corpus trapezoideum. 
d. Corpora pyramidalia. 
e. Crura cerebri. 
f. Corpus albicans. 
g. Infundibulum. 
h. Pituitary gland. 
1 a. Natiform protuberance, giving off the external root of the olfactory nerve. 
1 b. Pyriform protuberance, forming the origin of the internal root of the ol- 
factory nerve. 
1 c. Medullary root of the olfactory nerve emerging from a longitudinal fissure 
in the natiform protuberance. 
i. Fissure dividing the external root of olfactory nerve from the superincum- 
bent hemisphere. 
2. Chiasma of the optic nerves. 
3. Third pair of nerves. 
4. Fourth pair of nerves. 
5. Fifth pair of nerves. 
6. Sixth pair of nerves. 
k. Corpus trapezoideum. 
/. Corpus callosum, or commissure of the hemispheres. 
m. Fornix, or commissure of the hippocampi. 
n . Hippocampus major. 
o. Taenia hippocampi. 
o'. Anterior fibres of the taenia hippocampi continued into the anterior lobes 
of the hemispheres. 
p. Plexus choroides. 
q. Septum lucidum, or internal wall of the lateral ventricle (Plate VII. fig. 5.). 
r. Corpus striatum. 
s. Continuation of the lateral ventricle into the olfactory nerve. 
t. Optic thalami. 
u. Pineal gland. 
x. Part of a thin stratum of medullary fibres arching over the hippocampus 
major, and continued into the internal wall of the ventricle. 
