NEKVOUS SYSTEM. VERTEBRATA. 191 



ventral surface of the hemisphere, on the mesial side of a 

 depressed area corresponding to the nucleus amygdala?. 



The simple cerebellum is slightly more elaborated th;in 

 that of Peramelesj so that it comes to more closely resemble 

 that of Sarcophilus. It has sessile flocculi (comp. figs. 65 

 and 52). 



In the dissected specimen (fig. 66), the lateral ventricle is 

 prolonged forward to communicate by a narrow channel with 

 the large cavity in the olfactory bulb. The hippocampus is 

 placed in the caudal part of the chief cavity, and does not 

 extend so far forward as in the Marsupial (compare the 

 Wallaby's brain, D. 210). The meaning of this is that when 

 the corpus callosum makes its appearance (as it does for the 

 first time in the Eutheria), the cephalic extremity of the 



Fig. 66. (xli) 



HIP. 



hippocampus becomes reduced to a mere vestige lying partly 

 upon the upper surface of the corpus callosum and partly in 

 front of the latter body. The existence of a corpus callosum 

 and the vestigial nature of the anterior part of the hippo- 

 campal arc are the great distinguishing features of the 

 Eutherian brain, when compared with that of Marsupials 

 and Monotremes. 



Flatau and Jacobsohn, Vergl. Anat. d. Centralnerv. 

 1900, p. 341). 



Ganser, Morph. Jahrb., Bd. vii. 1882, p. 591. 



Elliot Smith, Journ. Anat. & Phys., vol. xxxii. 1897, 

 p. -44. 



D. 231. A cast of the cranial cavity of a Hedgehog (Erinaceus 

 europceus) . 



Shows the exact size and shape of the cerebral hemi- 

 spheres and olfactory bulbs. 



