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1&8 
on removing the thin cranial roof. In it there is situated a large 
superior longitudinal sinus, which opens on either side posteriorly 
into a lateral sinus lying between the cerebellum and cerebrum 
Whether this lateral sinus is drained mainly through the “ mas- 
toid” foramen, as in Perameles, or through the jugular foramen, 
as in most mammals, I was unable to determine. On removing 
the dura mater the cerebrum is exposed, as well as the relatively 
enormous olfactory bulb placed directly in front of each hemi- 
sphere. Posteriorly a narrow triangular gap is left between the 
two cerebral hemispheres and the cerebellum. When the dura 
mater is removed from this interval a crucial sulcus will be 
observed upon the dorsal aspect of the mesencephalon in its 
depths, corresponding to the divisions between the corpora quadri- 
gemina. A similar appearance is to be found in Perameles. The 
interval is not so marked in other Marsupials, and in some, such 
as Petaurus, very little, if anything, of the mesencephalon can be 
seen until the cerebral hemispheres are divaricated. Laterally in 
Notoryctes each cerebral hemisphere only just touches the anterior 
border of the cerebellum. This, coupled with the fact that there 
is a very slight divergence of the hemispheres posteriorly, leaves 
the corpora quadrigemina partly exposed. In all Marsupials the 
mesencephalon can be seen to a very slight extent when the dura 
mater is removed from the brain in situ, and in Wotorcytes and 
Perameles this exposure of the corpora quadrigemina is more 
marked than in others. This is opposed to the opinion of Sir 
William Turner, who says (40) that in all Marsupials, as in 
Edentata, Insectivora, Cheiroptera, and Rodentia, the mesen- 
cephalon is quite hidden by the cerebrum. Forbes (12) in 
Phascolarctos, and Beddard (1) in Thylacinus, admit that the 
corpora quadrigemina are partially exposed. 
The roof of the cranium is so thin and translucent that, with- 
out removing it, the dorsal aspect of the cerebrum may be seen. 
Thus in Dr. Stirling’s (38), figure 1, plate vil., the roof of the 
cranium is seen to be mapped out into four areas by a dark cross, 
which corresponds to a well-marked thickening of the bone in- 
ternally along these lines. The transverse marking corresponds 
to the line of separation of the olfactory bulbs from the cerebral 
hemispheres. It will be noticed that, as a result of the large 
relative size of the bulbs, this line is placed very far back— 
opposite the mid-point of the zygomatic arch. 
-To remove the brain, the olfactory peduncles were first incised, 
and the lobes were then readily raised and removed. The 
mesencephalon was then divided, and the cerebrum easily wedged 
out of the cranium. In this process the infundibular region of 
the floor of the third ventricle was, unfortunately, damaged, so 
that it was impossible to determine whether any trace of optic 
