554 
posterior margin, as far as which the posterior cerebral lobes ex- 
tended. The inferior vermiform process projected beyond the cere- 
bellar hemispheres, which were comparatively feebly developed. 
The Cetacea possess, not only in their great mass of brain, but in 
the number and complexity of the convolutions of their hemispheres, 
very decided evidences of a high degree of cerebral organisation. 
Professor Goodsir has allowed me to examine the brains of a por- 
poise, a bottle- nosed dolphin (Zh Tursio ), and a rorqual ( Balce - 
noptera ), either in his possession, or in the Anatomical Museum. 
In all. in accordance with the peculiar antero-posterior compression 
of the cranial cavity, the corresponding diameter of the cerebral 
hemispheres was very much shortened, so that the brain was widened 
out, and heightened greatly in its vertical diameter. In all, the 
distinction between the tentorial and occipital surfaces of the cere- 
bellum was very clearly marked. The cerebrum passed backwards 
as far as the posterior margin of the cerebellum. The cerebellum 
in them was a cerebellum inferius ; for, as far as could be judged 
from an inspection of the brains, as they lay out of their cavities, 
the cerebellum was not exposed when looked at from above. 
The cerebrum possessed very decided posterior lobes; for, on 
account of the great extent of the tentorial surface of the cere- 
bellum, and the heaping up of the cerebral convolutions in the 
vertical diameter, a large proportion of the cerebral hemi- 
spheres was placed above the cerebellum.* The brain of the bottle- 
nosed dolphin had been lying for many years in spirit in the Anato- 
mical Museum. A section had been made into the lateral ventricle 
on the right side, from which it appeared as if there were indica- 
tions of a prolongation of the ventricle in the direction of the pos- 
terior lobe. When the dissection was extended, so as to obtain a 
more complete view of the arrangement, it was seen that the lateral 
ventricle was continued backwards and outwards, sweeping along 
the posterior part of the optic thalamus. It then changed its direc- 
tion, and passed downwards and forwards, so as to form the inferior 
horn. At, or about, the spot where this change took place, a recess, 
extending backwards in the substance of the cerebral mass was met 
* Each hemisphere of Delphinus Tursio , measured 5 inches and x e ^ths in its 
antero-posterior diameter. The cerebrum extended 2 inches and x %ths behind 
the posterior end of the corpus callosum, the inferior surface of which mass of 
cerebrum was in relation to the tentorial surface of the cerebellum. 
