NERVOUS SYSTEM. VERTEBRATA. 199 



Family CHINCHILLIDJE. 



D. 249. The brain of a Viscacha (Viscaccia maxima) , in which 

 the right cerebral hemisphere has been dissected to expose 

 the hippocampus from above. 



There is a vertically-placed, somewhat arched, deep 

 sulcus above the mid-point of the rhinal fissure, but not 

 communicating with it. It may be regarded as the repre- 

 sentative of the sulcus in the brain of Dolichotis (figs. 74, 

 75, s), which has been called Sylvio-suprasylvian ; in 

 other words, it is the suprasylvian sulcus or the Prosimian 

 Sylvian. 



In front of this sulcus the hemisphere gradually tapers 

 to a narrow anterior extremity, and behind the sulcus the 

 hemisphere suddenly broadens. 



There are two well-marked sagittal sulci representing 

 the corono-lateral complex. According to Beddard other 

 sulci may occur. 0. C. 1323 E/. 



Beddard, Proc. Zool. Soc. 1892, p. 599. 



D. 250. The brain of a Viscacha (Viscacda maxima). 



O.C. 1323 G#. 



D. 251. The brain of a Common Chinchilla (Chinchilla lanigera). 



The pallium is apparently devoid of sulci. It is, 



however, hidden to some extent in this specimen by the 



membranes, in which the middle cerebral artery is very 



prominent. 0. C. 1323 Eg. 



Family DASYPROCTIDJE. 



D. 252. The brain of an Agouti (Dasyprocta aguti). 



In contradistinction to the flattening which charac- 

 terizes the basal region of the hemispheres in many 

 Rodents, the pyriform lobe and olfactory tubercle in 

 this specimen present the plump, rounded features which 

 distinguish these regions in macrosmatic brains of other 

 Orders. 



A deep and well-defined sulcus indents almost the whole 

 length of the hemisphere parallel to and a short distance 



