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Show 18 MR. F. E. BEDDARD ON TIIE [Jan. 20, §. The Brain of C y n o p it h e c u s n ig e r . I have been able to examine a single brain of the Celebesian Ape, of which drawings are exhibited herewith (text-figs. 7, 8, p. 19). The Simian fissure runs completely across and contributes to a perfect operculum, as in the Macaques. But the brain of Cynopithecus differs from the brains of the latter and agrees with that of Semnopithecus in the fact that the infraparietal fissure of each side bends sharply outwards before joining the Simian fissure; this suggests an exposure of the parieto-occipital, and a very faint groove (better marked upon the left side) is probably to be looked upon as a representative of this. The lateral occijrital sulcus is a single fissure, that is to say, it has not the Y-shape exhibited in so many monkeys. There is, however, a faint depression suggesting the upper arm of this Y. The inferior occipital sulcus is in some respects rather peculiar. Dr. Elliot Smith has justly pointed out1 that in Semnopithecus 11 the inferior occipital sulcus has dwindled to most insignificant proportions, and unless the student examines a large series of brains he will hardly recognize in the little arc around the lower end of the Simian sulcus the representative of the deep operculated infra-occipital sulcus in the Macaques." Cynopithecus niger has an even smaller semicircular representative of this furrow, which just arches round the lateral termination of the Simian fissure, and is nowhere near to reaching the posterior extremity of the occipital lobe. Further than this, a straight furrow, either connected (left side) or nearly connected (right side) with this, runs down the temporal lobe for some distance, exactly parallel with and between the parallel and collateral sulci. This I take to be the inferior temporal sulcus of brain anatomists. In the Macaques and Cercopitheci this sulcus is (so far as my own experience goes) quite constantly represented by a short furrow at the lower end of the temporal lobe, and this furrow is a marked character of those brains, and of Cercocebus and Cyno-cephalus. This more ventral ly placed furrow is not to be seen in my specimen of Cynopithecus. The existence of an upper portion of the inferior temporal sulcus is not, however, absolutely distinctive of Cynopithecus. It is indicated in a brain of Cynocephalus mormon which I have at my disposal, and in Kcisalis and Semnopithecus. In a brain of Cynocephalus porcarius this furrow is as well developed as in Cynopithecus, but on one side only (the right). But, with this exception, the furrow is nowhere so fully developed as in Cynopithecus. So far, therefore, it appears to be characteristic of this genus. It is, however, apparently impossible to lay much stress upon the reduced inferior occipital sulcus of Cynopithecus as a point of resemblance to Semnopithecus in the absence of a large series of brains of the former genus. Messrs. Kiikenthal and Ziehen figure a brain of Cynocephalus sphinx in which the fissure is fully as reduced as it is in Cynopithecus or Semnopithecus. I have already pointed out (supra, p. 12 foot- 1 Cat, Phys. Series Mus. Roy. Coll. Surg. vol. ii. p. 426. |