NERVOUS SYSTEM. VERTEBRATA. 481 



Apes. It consists of a small mesially-placed flocculus, 

 consisting of a series of simple folia grouped around the 

 auditory nerve, and a very large external paraflocculus. The 

 latter consists of the usual two parts, viz., a dorsal (lateral) 

 paraflocculus composed of broad flattened folia, and a 

 ventral (mesial) paraflocculus composed of narrower folia. 

 From the angle of junction of dorsal and ventral lobules a 

 large strongly-projecting feather-like group of paraflocctilar 

 folia projects to form the pedunculated petrosal lobule 

 (fig. 245). 0. C. 1338 G !>. 



D. 647. Two casts of the cranial cavity of a Siamang (Hy locates 



syndactylus) , 



D. 648. The left cerebral hemisphere and the rest of the brain 

 of a young Mias or Orang-Outang (Simla satyrus). 



In comparison with those of other Apes the brains 

 of the Anthropoids are characterized by their greater 

 absolute dimensions. The cerebral hemispheres are fuller 

 and more rounded than those of Hylobates, and especially 

 so in the frontal region. There is, however, a very pro- 

 nounced rostration of the orbital region resulting in the 

 formation of a most prominent keel. The floccular lobes 

 of the cerebellum (and more especially the paraflocculus) 

 undergo a noteworthy reduction in size. The trapezoid 

 bodies become covered by the pons to a much greater 

 extent than is the case in other Apes; and also, partly, as a 

 result of the increasing breadth of the pons, the large 

 olivary bodies now extend as far as the latter body. 



But by far the most important changes are found in the 

 cerebral hemispheres, the surfaces of which are much more 

 extensive, and consequently much more richly supplied 

 with sulci than is the case in lower Apes. 



The anterior insular region presents features such as have 

 been already described in the Gibbons. The fron to-orbital 

 (anterior limiting) sulcus is deep and very long, extending 

 across the orbital margin so as almost to meet the inferior 

 precentral (arcuate) sulcus. The exposed portion of the 

 superior limiting (opercular) sulcus is also deep and long, 

 but is still separated from the fronto-orbital by a broad 



