On the Cranial Nerves of Elasmolranch Fishes. 531 



the common root arches backwards, and enters a large foramen along 

 with the auditory nerve. Leaving the auditory, it runs forwards 

 through a canal in front of the auditory capsule. Having proceeded 

 some distance (about 5 cm. in a large fish), it divides into two branches, 

 a large branch (the hyomandibular) that proceeds outwards behind 

 the spiracle, and a smaller branch (the palatine), which bends down- 

 wards towards the roof of the mouth. When the common trunk of 

 these nerves is carefully studied, it is found to consist of two separate 

 bundles, a small bundle which seems to be continuous with the 

 palatine nerve, and a larger bundle which is continuous with the 

 hyomandibular nerve. At the point of bifurcation there is a large 

 collection of ganglionic cells, some of which lie in the palatine nerve 

 and may be known as the palatine ganglion. Further, the two 

 nerves are connected in front of the apparently compound ganglion 

 by a number of fibres which have a somewhat plexiform arrange- 

 ment. 



6. The Palatine Nerve. This nerve (6, fig*. 1) at once gives off a 

 number of branches (prespiracular) which are distributed to the 

 tissues in front of the spiracle. The main trunk sends numerous 

 branches to the roof of the mouth. Continuous with what may be 

 known as the root of the palatine nerve, a distinct bundle of fibres 

 runs outwards under the hyomandibular nerve (from which it receives 

 one or more small branches), and passing over the hyomandibular 

 cartilage, runs forwards to end in the fold of mucous membrane lying 

 between the hyoidean and mandibular cartilages. I look upon this 

 long slender nerve as corresponding to the chorda tympani of higher 

 vertebrates. 



7. The Hyomandibular Nerve. This nerve (7, fig. 1) which increases 

 immensely in size, beyond the ganglion, is chiefly concerned in supply- 

 ing the large group of ampullae that lies external to the spiracle, but 

 it also supplies the mucous canals not already referred to, with the 

 exception of the aural mucous canal and the canal of the lateral line. 

 It further sends a branch backwards to muscles lying over and within 

 the hyomandibular cartilage and the branchial apparatus. 



In describing the facial complex, I have referred to a special 

 ganglion on the ophthalmicus superficialis, to another on the buccal, 

 and to a compound ganglion in connexion with the hyomandibnlar 

 and palatine nerves. Gegenbaur considers the palatine nerve of Blas- 

 mobranchs as homologous with the great petrosal nerve of mammals. 

 ]f this comparison holds, which I have every reason to believe it will, 

 the interesting question arises Is there any relation between the 

 palatine ganglion of the Elasmobranch and the spheno-palatine gan- 

 glion of the mammal ? And this leads to the further question 

 Are the ganglia of the ophthalmicus superficialis, buccal, and hyoman- 

 dibular nerves related to the geniculate, otic, and submaxillary ganglia 



