RAIA. 



323 



Fig. 230. — The Ear (Mem- 

 branous Labyrinth) of the 

 Skate (Diagrammatic). 



Semi-circular Canal. 



Utriculus. 



The auditory nerve is simple and short and passes to 

 the auditory capsule. 



If the jugular sinus be cut 

 open throughout its length 

 the glossopharyngeal (IX.) 

 and vagus (X.) nerves will 

 easily be exposed. The IXth 

 is simple and passes from 

 behind the auditory capsule 

 to the first gill-slit. 



The vagus (X.) has four 

 branchial branches to the 

 four last gill-slits, a lateral 

 line branch under the skin 

 and a visceral branch which 

 passes to the heart and 

 stomach. 



The spinal cord gives 

 off paired spinal nerves^ the 

 first fifteen (or 15 to 18) of 



which join together to form the brachial plexus^ passing to 

 the pectoral fin. 



Ampulla. 



Lagena. 



Horizontal 



Semi-circular 



Canal. 



Sacculus. 



Note that there is no middle or outer 

 ear, and that the inner ear communicates 

 by a duct to the exterior. 



We may summarise the cranial nerves as follows :- 



FOR E-BRA /JV. MID-BRA IN. 



I. Olfactory. 

 II. Optic. 



III. Oculomotor. 



IV. Trochlear. 



V. Trigeminal. 



1. Part of ophthalmicus 



superficialis. 



2. Ophthalmicus profun- 



dus. 



3. Maxillary. 



4. Mandibular. 



VI. Abducens. 



HIND BRAIN. 



VII. Facial. 



1. Part of ophthalmicus 



superficialis. 



2. Hyomandibular. 



3. Outer bjiccal* 



4. Inner buccal, f 



5. Palatine (and pre- 



spiracular). 



VIII. Auditory. 

 IX. Glossopharyngeal. 



X. Vagus. 



1. Fo7cr branchiah. 



2. LatcT-al line. 



3. Visceral. 



* The branches in italic type disappear in Vertebrata above the fishes, besides 

 parts of other branches. 



t The maxillary anast moses to some extent with the inner buccal nerve, but 

 whether fibres of V. actually supply the ampulla; at the termination of the inner 

 buccal is doubtful. 



