158 



ZOOLOGY 



capsule. The diencephalon {ZH) is comparatively small ; its roof 

 is very thin, while the floor is composed of two thickish masses 



Fig. 821. — Brain of Scyllium canicula. A, dorsal view; B, ventral view; C, lateral view. 

 F. rho. fossa rliomboidalis (fourth ventricle) ; Gp, epiphysis ; ////, cerebellum ; BS. II, hypo- 

 physis ; L. ol. olfactory bulb ; Mff, mid-brain ; NH, medulla oblongata ; Sv, saccus vasculosus ; 

 Tto, olfactory peduncle ; l/L, lobi inferiores ; VII, prosencephalon ; ZII^ diencephalon ; 

 //> optic nerves; III, oculomotor; /K, pathetic; K, trigeminal ; VI, abducent; yil, facial; 

 FIIIj auditory ; /.Y, glossopharyngeal ; X, vagus. (From Wiedersheim's Cooip. Anatoray.) 



— the Optic thalami. Attached to the roof is a slender tube 

 the epij^hysis cerebri or -pineal hocly (Gj).), which runs forwards and 



