NERVES OF THE DOGFISH 349 



and the section of the canal innervated by the glossopharyngeus. 

 About five ramuli are contributed to canal organs (fig. 50, 

 ot. VII) 



Hawkes finds a ramus oticus in Chlamydoselachus that sup- 

 plies the postorbital section of the infra-orbital canal, and the 

 horizontal section of the infra-orbital canal (anterior end of the 

 main lateral-line canal), and also sends two small branches to 

 the skin. These latter she interprets as general cutaneous. 

 But comparison with Squalus would suggest that in Chlamydo- 

 selachus these cutaneous branches may possibly innervate 

 spiracular organs as in Squalus, or isolated neuromasts, pit- 

 organs. 



Besides innervating canal organs in Squalus, the ramus oticus 

 supplies a peculiar tubular organ on the anterior mesial wall of 

 the spiracle (fig. 20, ospr.). This is apparently a modified 

 ampulla of Lorenzini. 



Landacre describes in the 22-mm. embryo a lateral-line pri- 

 mordium which he regards as corresponding to the most poste- 

 rior sense-organs of the infra-orbital canal. This receives two 

 small branches from the buccalis ganglion, arising in the angle 

 between the buccalis and the r. oph. spf. VII. He describes 

 a second small twig arising more posteriorly, which innervates 

 a lateral-line primordium that he believes gives rise to lateral- 

 line organs near the junction of the supra-orbital and infra- 

 orbital canals. He considers this the ramus oticus auctorum. 

 He notes that this ramus after supplying twigs to the lateral- 

 line primordium sends a branch more posteriorly, ending in the 

 anterior wall of the spiracle. 



As stated in a preceding section, the ramus oticus VII in Mus- 

 telus arises from a ganglionic mass in common with "the small 

 nerves that innervate the postorbital section of the infra- 

 orbital canal. An account of the occurrence, innervation, and 

 homologies of the spiracular organ of elasmobranchs, ganoids, 

 and dipnoans has been given elsewhere by the writers ('20). 



Herrick ('99) considers the ramus oticus of Menidia as primi- 

 tively a general cutaneous dorsal ramus of the facialis to which 



