1891.] 



DOLICHOTIS PATAGONICA. 



243 



the Sylvian fissure is very deep ; it passes forwards and then back- 

 wards, forming a line which is convex anteriorly ; after this it bends 

 forwards at a sharp angle and nearly joins the principal longitudinal 

 sulcus (see fig. 4). The upper surface of each cerebral hemi- 

 sphere is marked by a strong sulcus running with a sinuous 

 outline approximately parallel to the long axis of the brain ; these 

 sulci commence a little way in front of the hinder margin of the 



Fig. 4. 



Brain of Bolichotis fatagonica. 

 A, from the side ; B, from above : 8, sylvian fissure ; R, rhinal fissure. 



brain ; anteriorly each bends outwards and joins the rhinal sulcus ; 

 the other fissures are of less importance and are illustrated in the 

 drawing exhibited (fig. 4). 



I have been able to compare the brain of this species with those 

 of the following Rodents at present in my possession : — 

 Castor fiber (a cast of the brain ^), 



"^ For this and several other casts of the brain itself, not of the cranial 

 cavity, I am greatly indebted to Prof. d'Arcy Thompson. 



16* 



