154 



ZOOLOGY 



SECT. 



The fourth ventricle or metacoele (Fig. 832, meta.) is continuous 

 behind with the central canal of the spinal cord. It gives off an 

 epicoele above, and in front is continuous with a narrow passage, 





X 



FIG. 831. Brain of Scyllium canicula. A, dorsal view ; B, ventral view ; C, lateral view. 

 F. rho. fossa rhombohlalis (fourth ventricle) ; Gp, epiphysis ; HH, cerebellum ; HS. H, hypo- 

 physis ; L. ol. olfactory bulb ; MH, mid-brain ; NH, medulla oblongata ; Si', saccus vascu- 

 losus ; Tro, olfactory peduncle ; UL, lobi iuferiores ; VH, prosencephalon ; ZH, dien- 

 cephalon ; II, optic nerves ; ///, oculomotor ; IV, pathetic ; V, trigeminal ; VI, abducent ; 

 VII, facial ; VIII, auditory ; IX, glossopharyngeal ; X, vagus. (From Wiedersheim's 

 Comp. Anatomy.) 



the iler or mesocoele (iter.), which opens anteriorly into a wider 

 space, the diaccele or third ventricle (dia.), occupying the interior of 



