NERVOUS SYSTEM. VERTEBBATA. 241 



Note the pear-shaped ganglion habenulse and the tsenia 

 thalami ; the habenular commissure, the pineal body, and 

 the posterior commissure forming the upper lip of the 

 opening of the aqueduct of Sylvius. The latter is a large 

 canal, which expands posteriorly into a trumpet-shape. 



The most noteworthy features upon the lateral aspect of 

 the mid-brain are the huge size of the mesial (posterior) 

 geniculate body and the prominence of the posterior quadri- 

 geminal bodies. Both phenomena are probably related to 

 the acuteness of hearing in Cats. 



There is an extremely well-defined tractus peduncular is 

 trans versus. 



The pons, anterior pyramids, and trapezoid bodies are 

 exceedingly clearly defined, and a slight olivary eminence 

 now makes its appearance at the lateral border of the 

 pyramid. All the cranial nerves are well-developed and 

 present the typical relations. 



The cerebellum presents features closely resembling the 

 corresponding organ in the larger Edentates and in some 

 of the Rodents. 



There is a large floccular lobe closely applied to the 

 lateral aspect of the middle (or pontine) peduncle of the 

 cerebellum and the tuberculum acusticum. The latter is 

 easily recognised by the insertion of the auditory nerve. 

 The floccular lobe consists of three parts, viz. : A flattened 

 body, the flocculus (sensu stricto), closely applied to the 

 surface of the acoustic tubercle ; a horizontal multifoliate 

 band, the ventral paraflocculus, immediately external to 

 this ; and the dorsal paraflocculus, also a horizontal vermi- 

 form band continuous anteriorly with the ventral para- 

 flocculus and posteriorly prolonged into continuity with 

 the pyramid (a part of the general mass of the cerebellum). 



The floccular lobes are separated from the general mass 

 of the cerebellum by deep floccular fissures. [A similar 

 floccular lobe may be seen to better advantage in Myrme- 

 copliaga (specimen D. 282) : the fundamental plan is ex- 

 plained by a series o diagrams in the account o Cabassous 

 (specimen D. 268).] 



The interfloccular mass of the cerebellum may be sub- 

 divided for descriptive purposes into three main parts or 

 azygos lobes. 



VOL. II. R 



