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Show 148 ON THE BBAIN IN THE LEMUBS [Feb. 19, family by itself. Its most marked characters are (1) the production of a large semicircular sulcus by the fusion of the Sylvian with the parieto-occipital fissures *: (2) the length of the angular sulcus which blends in front with the infero-frontal and gives off two branches, one running downwards parallel with the Sylvian fissure, the other running inwards towards the middle line2. The former character is the most distinctive; for the long angular sulcus fused with the infero-frontal is met with in the Lemurine, and there are in them and in other Lemurs traces of the two branches in the presylvian fissure, and in the indentation to which I have referred as lying in the widest part of the sagittal gyrus. As to Tarsius, it has so smooth a brain that no inferences can be drawn. There remains the family Lemurida?, of which four subfamilies are commonly allowed, viz., Lemurince, Indrisince, Galaginince, and Lorisince. The first mentioned subfamily has a very uniform type of brain-structure. The differences between Hapalemur and Lemur, which I indicated some years since, are removed by the examination of a larger series of brains of Lemur. Indeed the only difference which I thought myself justified in pointing out was the continuity in Hapalemur of the angular and infero-frontal fissures ; but, as I have mentioned in the present paper, the continuity is more marked in Lemur mongoz. The Lorisince, on the other hand, do not form so natural an assemblage as do the Lemurince. It seems as if w e had in this group the few remnants of a formerly much larger series-a suggestion which is borne out by their wide and scattered distribution. They all, however, agree to differ from the Lemurince in the shortness or even rudimentary character of the angular and infero-frontal fissures, which do not nearly meet, aud in the presence of the parieto-occipital fissure near the middle line of the brain. These remarks, of course, hardly apply to the small and smooth brain of Loris. The Galaginince have as their most distinctive character the absence or feeble development of the antero-temporal fissure. They seem to be most like the Lorisince in other characters. They resemble them in the shortness of the angular fissure, and Galago has a further point of likeness to Perodicticus and Nycticebus in the cross-like parieto-occipital structure. In all the Indrisince figured by Milne-Edwards this last mentioned fissure is well marked. But as I have not examined the brains of any of this group, I do not venture upon the expression of any opinion as to their affinities. 1 They are separated according to Oudemans. 2 Or nearly; see Oudemans, loc. cit. pi. iii. figs. 12, 14. |