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Show 802 ON THE BRAIN OF HYDROCH02RUS. [June 20, The third fissure c, which runs parallel or approximately so to the last, is also a perfectly constant fissure in the Capybara's brain. The temporal lobe has further other slight fissures which are so irregular that I think it hardly worth the trouble of describing them. Fig. 4. Brain of Hydrochcerus, inner view of hemispheres. Now we come to the fissure d of my former paper on the Rodent's brain. In one of the three brains at m y disposal it passes outward and forward from the fissure a on both sides, or rather from the margin of the knee-shaped bridging convolution, already referred to. If this region of the brain be compared with m y figure of that of Gulo, a striking likeness will be apparent, suggesting that the fissure d is the crucial sulcus of the Carnivora. In the two other brains the fissure was not so clearly marked. Sylvian fissure.-Dareste has remarked that this fissure appears to be absent in the Capybara. It is certainly not at all plain in any of the three brains which I have examined myself. But nevertheless I do not think that it can be said to be totally un- Fig. 5. Brain of Hydrochcerus, inner view. Nat. size. A , calcarine (?) fissure : B, C, parieto-occipital; E. calloso-margiual. represented. On viewing all these brains from the dorsal aspect a prominent and obliquely (or, in one case, transversely) running fissure is to be seen which separates off the wider posterior region of the hemispheres from the anterior narrower portion (fio- 1 s) It coincides, in fact, in position and direction with what seems to be undoubtedly the Sylvian fissure in Lagostomus (P. Z. S. 1892 p 599 |