128 



O'S THE BKOAD-NOSED LEMUB, 



[Feb. 19, 



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 way 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 H. simus than in the other 

 species ; but this particular feature is sometimes lost during 

 preservation. However, this aud 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), Sj'lvian fissure. 

 (From P. Z. S. 1891, p. 457.) 



The antero-temporal fissure also differs slightly in its form. In 

 H. griseus this fissure is sometimes broken into two, the upper 

 piece joining the top of the Sylvian, as I have figured. In //. simus 

 the fissure is not thus broken, but the upper end, which corresponds 

 to the detached piece in H. 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 Lemtir, which comes of course very 

 close to Hapalemur, some species show a continuity and others 

 a discontinuity between these two fissures. So, too, does this 

 genus Hapalemur. In H. 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 con- 

 tinuous 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 



