NERVOUS SYSTEM. VERTEBRATA. 383 



fissure by which it is bounded becomes much fainter as the 

 Sylvian vallecula is approached. 0. C. 1337 c a. 



Presented by C. E. Flower, Esq. 



D. 551. The brain of a Black-eared Marmoset (ffapalepenicillata). 

 The left hemisphere has been separated. 



This is a more carefully-preserved specimen than any of 

 the others, and not only are all parts of the brain preserved 

 intact, but they all retain their natural shapes. 



Thus the true proportions of the small ellipsoidal olfactory 

 bulb and its exceedingly delicate ribbon-like peduncle can 

 be appreciated. The (external) olfactory tract is very 

 distinct (as, in fact, is the case in all Anthropoidea), pursuing 

 its backward course in the olfactory peduncle, then skirting 

 the lateral edge of the tuberculum olfactorium (which is 

 still recognisable as such, in spite of its diminutive pro- 

 portions), and finally disappearing in the vallecula Sylvii to 

 reach the posterior part of the pyriform lobe. The rhinal 

 fissure indicates the lateral boundary of the latter. 



It is a peculiarity of all the Anthropoidea that these 

 olfactory areas of the brain are greatly reduced in com- 

 parison with those of other Mammals. For in Man and 

 Monkeys the sense of smell loses the predominant role which 

 it exercises in most other (non-aquatic) Mammals. The 

 Sylvian fissure, the simple orbital, parallel, calcarine, and 

 the faint trace of the calloso-marginal sulci need only be 

 mentioned. There is, however, an oblique sulcus on the 

 ventral surface, which probably represents the collateral 

 sulcus. 



The features of the corpus callosum, the diminutive 

 psalterium, the anterior commissure, the lamina terminalis, 

 the optic chiasma, and the cerebellum are beautifully 

 demonstrated in this specimen. 



D. 552. The brain of a Common Marmoset (Hapale jacchun). 



The intraparietal sulcus is absent (or possibly represented 

 by an almost imperceptible depression in the left hemi- 

 sphere) ; the parallel sulcus is very faint ; and on the mesial 

 aspect there is a sulcus in a corresponding position to that 



