CRANIAL NERVES OF SKATE 599 



nasal capsule, to inner buccal ampullae. The 

 outer buccal runs under the eye, external to the 

 olfactory capsule, to outer buccal ampulla. 



3. The large hyomandibular runs directly outwards 



behind the spiracle to hyoid ampullae. It gives 

 off minor hyoidean nerves. 



4. The external mandibular runs behind and outside 



of the mandibular muscle to mandibular ampuhso, 

 and is a branch of the hyo-mandibular. 



5. The palatine descends in front of the spiracle to the 



roof of the mouth. Close beside it there is a 

 prespiracular. 



6. The " facial proper," apparently arising from 3, 



supplies the muscles of the hyoid arch. 



7. The " chorda tympani," apparently arising from 3, 



runs under the spiracle to the inner side of the 

 jaw. 



With the loss of the sensory ampullae, the seventh 

 nerve of higher Vertebrates becomes restricted to 

 the last three branches (5, 6, and 7). 



A recurrent branch of the facial also runs external 

 to the auditory capsule to IX., and is equivalent 

 to Jacobson's anastomosis in higher forms. 



VIII. The auditory, arising just behind VII., is the nerve 

 of the ear. 

 IX. The glossopharyngeal, the most typical of all, is the 

 nerve of the first functional gill-cleft. Its root 

 passes through the floor of the auditory capsule, 

 and bears a ganglion above the cleft. Its 

 branches, as named by Beard, are : — 



1. Post -branchial, to the muscles of the first branchial 



arch ; 



2. Pre -branchial, arches over the cleft and runs along 



its front wall ; 



3. Intestinal or visceral, to the pharynx ; 



4. Supra-branchial or dorsal, to a few sense organs on 



the mid-dorsal line of the head. 



X. The vagus, apparently made \ip of several cranial 

 nerves, has numerous roots, and divides into six 

 main ganglionated portions, which supply the 

 four posterior clefts and arches, the posterior 

 jelly-tubes, and the heart and stomach. It thus 

 consists of : — 



I. Ganglionated roots with nerves to the clefts and 

 arches (2 to 5 inclusive), with post -branchial, 

 pre -branchial, and pharyngeal branches as in IX^ 



