| OCR Text |
Show 128 ON THE BROAD-NOSED LEMUR. [Feb. 10. end is at least slightly hooked. This was more marked upon the right than upon the left side. The olfactory region of the brain was much compressed ventrally in the w ay which characterizes so many Apes. It presents the appearance of having been squeezed between the fingers while in a plastic condition. The compression seemed to me to be more marked in II. simus than in the other species ; but this particular feature is sometimes lost during preservation. However, this and the other brains were most carefully extracted from the skull; they have been but very slightly altered in shape during the process of hardening with alcohol. Text-fig. 25. Brain of Hapalemur griseus. A. From above. B. Lateral view. S (in both figures), Sylvian fissure. (From P. Z. S. 1891, p. 4-37.) The antero-temporal fissure also differs slightly in its form. In //. griseus this fissure is sometimes broken into two, the upper piece joining the top of the Sylvian, as I have figured. In II. simus the fissure is not thus broken, but the upper end. which corresponds to the detached piece in If. griseus, curved forward in a hook-like fashion and in a direction parallel to the end of the Sylvian fissure. In originally describing the brain of H. griseus I laid some emphasis upon the fact that the angular and the infero-frontal fissures form one continuous fissure. This emphasis is justified to some extent, since in other Lemurs the two fissures are quite distinct. But in the genus Lemur, which comes of course very close to Hapalemur, some species show a continuity and others a discontinuity between Ibese two fissures. So, too, does this genus Hapalemur. In /I. simus, as the drawing shows, the two fissures are not only discontinuous, but the two ends-the anterior of one and the posterior of the other-if continued in a straight line would hardly meet. This is quite different from what is found in H. griseus: in the first specimen of the brain of this animal which I studied, the two fissures were continuous at least on the left side, there being a faint gap on the right side of the brain ; but in a second example of this species |
