186 THE SPINY DOGFISH— THE SKATE 



to the under-surface of the medulla, where it arises between the roots 

 of nerves V and VII and the mid-ventral line. 

 Make a complete drawing of the brain, cranial nerves, and eye muscles. 



Olfactory capsule 



SupL ophthalmic 

 V & VII- 



Superior oblique 



Anterior rectus 

 Superior rectus' 



Inf. ophthalmic V 



I Posterior rectus 

 Xpculomotor UV 



Auditory capsule 

 Optic lobe 



Cerebellum' " 

 Corpora restiformia' 



Medulla oblongata' 



Inner buccal VII 

 .^Maxillary V 

 -Outer buccal 

 VII 



['Mandibular 



V 



Ext mand. 

 VII 



-Thalamencephalon 



Mandibulanl 



muscle \\ 



resp.VII 

 [Palatine Vlll 



Aecurrentfacial 



■Hyom. 

 VII 

 htjn. ' ~-,^"X-Hyoidean VII 

 Facial proper VII 



Branchial X 



Visceral X 



Fig. 63. — The Brain (dorsal view), Cranial Nerves, and Eye Muscles of the Skate {Raia). 



11. Optic nerve ; IV. Pathetic nerve ; VI. Abducent nerve ; Ext. mand. VII. External Mandibular branch of Facial 

 nerve ; Hyom. VII. Hyomandibular branch of Facial nerve ; Int. m. VII. Internal Mandibular branch of Facial 

 nerve ; Presp. VII. Prespiracular branch of Facial nerve ; VIII. Auditory nerve ; Spir. Spiracle. 



Examine one of the auditory organs or otocysts. Carefully remove the 

 cartilage of the auditory capsule of the skull until the parts of the otocyst are 

 exposed. It consists of three semicircular canals, an endolymphatic duct, 

 otoliths (limy matter) in the lower part, and endolymph throughout the cavity 

 and within the canals. Between the otocyst wall and the cartilaginous auditory 

 capsule is the perilymph. 



