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Show 600 MR. F. E. BEDDARD ON THE [Dec. 6, commences about 5 mm. from the posterior end of the brain and at about the same distance from the interhemispheral fissure ; this furrow is slightly oblique in direction, the anterior end being nearer to the middle line than the posterior. In front of this is another furrow, rather deeper but about the same length ; this furrow is twice the distance from the median fnrrow, that is the last described furrow, and shows a tendency (on one side) to bifurcate anteriorly. If the anterior end of the posterior furrow were bent away from the middle line of the brain, it would come to be continuous with the anterior longitudinal furrow; as it is a space of 3 m m . separates the two. Parallel with the posterior longitudinal furrow are two less conspicuous fissures ; they run at about equal distances from each other and from the furrow first described: the inner of the two is only just visible ; it is very short and very plainly marked : the outer is 10 m m . in length ; it starts from the posterior border of the hemisphere ; but the posterior part of this fissure is much shallower than the anterior half, and is indeed only plainly recognizable on the right hemisphere. The Sylvian fissure is very deep on the upper surface of the brain though shallow at its commencement; its direction is on the whole at right angles to the longitudinal axis of the brain; it is, however, curved, the convexity of the curve being forwards; at about the middle of its course it gives off a short forwardly running branch, the direction of which is also slightly downwards. On the under surface of the brain the only distinct fissure (apart from the Sylvian) to be seen is the rhinal fissure. This is quite obvious from end to end. This fissure can be traced back on the posterior aspect of the hemispheres up to within 6 or 7 m m . of the upper surface of the brain. Hystrix cristata1.-Total length 45 mm., breadth 36 mm., height 20 m m. The cerebral hemispheres are very broad and together have an almost circular contour. They diverge posteriorly so as to reveal the corpora quadrigemina. The upper surface is furrowed to some extent, though not to so marked a degree as in some other genera. The length of each hemisphere is 30 mm. A longitudinal furrow about 10 m m . long runs on either side of the median furrow on the posterior half of the hemisphere ; rather in front of the middle of each hemisphere, this furrow is very nearly continuous with a much deeper furrow passing obliquely outwards at an angle of about 30° with the transverse axis ; this furrow, which is about 13 mm. long, is restricted to the dorsal surface of the brain. The remaining furrows are decidedly asymmetrical in their arrangement. On the left half of the brain there are two downwardly directed fissures running parallel with the Sylvian fissure. O n the right 1 Figured by Leuret and Gratiolet (8, plate iii.). |