NERVOUS SYSTEM. VERTEBRATA. 389 



marked oblique sulcus crossing the inferior margin of the 

 hemisphere in the situation where a great inferior operculum 

 is found in many Cercopithecidse. Kukenthal and Ziehen 

 call it " inferior occipital/' But the presence of such a 

 sulcus in this brain clearly does away with the necessity for 

 a collateral sulcus. 0. C. 1337 D c. 



D. 557. The brain of a Masked Titi (Callithrix brunnea), (<$). 



This specimen closely resembles the last described. If 

 the lips of the Sylvian fissure be divaricated in either of 

 these brains a small, smooth, submerged area or insula will 

 be found. The anterior (fronto-parietal) is much more 

 extensive than the posterior (temporal) operculum. 



There is a short but definite central sulcus on the right 

 hemisphere. 



The manner in which the upper end of the parallel sulcus 

 approaches the Sylvian fissure (especially in the right hemi- 

 sphere) is very instructive, when we recall that in most 

 non-Primate brains the representatives of these two sulci 

 are united to form a suprasylvian arc. 



The calcarine complex is unbranched, as in Hapale. 



0. C. 1337 D b. 

 D. 558. The brain of an Orabassu Titi (Callithrix molocli). 



This closely resembles the last specimen. There is, how- 

 ever, no central sulcus. The simple calcarine sulcus is 

 clearly shown. 



D. 559. The brain of a Three-banded Dourocoli (Nyctipitliecus 

 trivirgatus), ( ? ) 



The right cerebral hemisphere has been separated from 

 the remainder of the encephalon. The left cerebral hemi- 

 sphere has been dissected so as to exhibit the principal 

 structures in the lateral ventricle ,- the descending and the 

 posterior cornua of the ventricle have been laid open, ex- 

 posing, in the former, the hippocampus major and the 

 fimbria and, in the latter which is prolonged into the 

 overhanging occipital lobe, a large calcar avis. 



The arrangement of the sulci resembles that in Chrysothrix 

 sciurea, and, less closely, that in Lemur. The pyriform 

 lobe is rather broader than in Chrysothrix, and the posterior 

 rhinal fissure is placed very low down on the lateral 



