66 MR. F. E. BEDDARD ON THE ENCEPHALIC [May 16, 
A noteworthy difference exists between the two specimens in 
relation to the course of the large left carotid. In the one 
brain this artery lies outside of the dura mater for a large part 
of its course, and gives off at least one branch to the brain which 
perforated that membrane ; thus giving additional proof of the 
fact that the carotid itself lies outside of the dura mater. In the 
other brain I did not observe this state of affairs. It follows 
that the left carotid exhibits an aloofness from the brain which 
is remarkable, and that the branches therefrom do not run on 
the same plane with it. 
The arteries to the optic lobes arise from the basilar artery after 
its bifurcation, between this point and the entrance of the carotids, 
and further back still there is a smaller cerebellar artery. The 
posterior cerebral artery is small and arises just in front of entrance 
of the carotids. The next important artery is a cerebral, which 
arises in front of the inflow of the carotids. This artery is the 
middle cerebral or Sylvian of other animals, since it runs along the 
rudimentary Sylvian fissure. The posterior cerebral is also partly 
represented by several small branches of the artery to the optic 
lobe. In front of the middle cerebral artery is a smaller anterior 
cerebral artery. 
Anteriorly to this the circle of Willis is completed in the 
following way: the large left carotid bifurcates to form the two 
nearly equally stout’ ophthalmic arteries which of course accom- 
pany the optic nerves. Just before this bifurcation the slender 
right carotid effects a junction with the common trunk. 
Immediately in front of this a single trunk arises from the point 
of bifurcation of the left carotid, which at once divides into two. 
These vessels run closely side by side in the furrow which separates 
the two hemispheres and rejoin at the extreme anterior end of the 
brain, their course in fact recalling that of the callosal arteries 
in mammals. The arteries are by no means inconspicuous, as 1s 
shown in the annexed figure (text-fig. 19, p. 65). 
T now draw, of course quite in a preliminary and tentative way, 
a series of comparisons between the Ophidian and Lacertilian 
brain arteries, enumerating the characters of the former in the 
same order as already given (on p. 64) for the latter. 
§ Cerebral Arteries in the Ophadia. 
(1) The entrance of the vertebral arteries into the anterior 
spinal marks the end of the medulla oblongata. These arteries 
seem to be stouter than in the Lacertilia. 
(2) There is no markedly large pair of cerebellar arteries arising 
from the basilar artery, but a number of more or less equisized 
arteries supplying the cerebellum and adjacent region. 
(3) The two branches produced by the bifurcation of the basilar 
are equisized. The anterior cerebellar arteries arise from the 
bifurcated region. 
(4) The point of entrance of the carotids appears to be rather 
