THE BRAIN IN MARSUPIAL ANIMALS. 
93 
corresponding parts to those performed by the placental Mammalia on a larger 
theatre, in which the avoidance of more numerous and powerful enemies, or the 
capture of more varied and subtle prey, demands the manifestation of more courage, 
the practice of more address, and the possession of more resources than appear to 
be called for by the exigencies of the Marsupiata in their more limited sphere. 
Fig 1. 
2 . 
3. 
4. 
5. 
6 . 
7 . 
8 . 
9. 
Fig. 1. 
2 . 
Description of the Plates. 
PLATE V. 
External form. 
The upper surface of the brain of a Beaver ( Castor Fiber, L.). 
The upper surface of the brain of a Monkey ( Midas nifimanus, Geoff.). 
The upper surface of the brain of a Wombat {Phascolomys Wombatus, Bl.). 
The upper surface of the brain of a Kangaroo ( Macropus major, Shaw.). 
The upper surface of the brain of an Ursine Dasyure ( Dasyurus ursinus, 
Geoff.). 
The upper surface of the brain of a Virginian Opossum ( Didelphys Virgi- 
niana, Shaw). 
The base of the brain of a Beaver. 
The base of the brain of a Wombat. 
The base of the brain of a Virginian Opossum. 
From these figures it will be seen that the convolution of the surface of 
the hemispheres of the brain does not take place in proportion as the 
hemispheres themselves are developed in superficial extent. They are 
fewer, for example, in the Midas, in which the hemispheres extend, as in 
most of the Quadrumana, over the greater part of the cerebellum, than 
in the Kangaroo or Wombat, where the cerebellum is left quite exposed. 
The brains of two species of herbivorous and two of carnivorous Marsu- 
pials are figured in this plate, to show indications of superior development 
which distinguish the brain of the herbivora, in the greater proportional 
development of the cerebrum, its convoluted surface, and the smaller 
proportional size of the olfactory tubercles. In all the species, but espe- 
cially the carnivorous Marsupials, the greater relative size of the vermi- 
form process is deserving of notice, as indicating the approach to the 
oviparous type of cerebral structure : it is associated with a corresponding 
diminution of the pons Varolii, as is strikingly shown in fig. 9. 
PLATE VI. 
Side view of the brain of the Kangaroo. 
Side view of the brain of the Virginian Opossum. 
