138 NERVE COMPONENTS OF BONY FISHES. 



caudad these remaining fibres from the r. opercnlaris VII 

 enter and innervate the m. levator opercuh (w. lev. op,). 



The motor fibres which continue cephalad from the 

 truncus hyomandibularis soon turn ventrally to reach the 

 dorsal surface of the very large m. adductor arcus palatini 

 (;;/. ad. a. p.)^ in which position they continue cephalad, 

 giving off twigs for the innervation of this muscle from 

 time to time. This ramus for the adductor arcus palatini 

 is larger than the entire dorsal portion of the r. opercularis 

 profundus. 



2. — The Ramus Opercnlaris Super ficialis VII. 



Immediately after the truncus hyomandibularis has 

 entered the canal in the hyomandibular bone it gives off 

 a ramus directed caudad, the r. opercularis superficialis 

 VII {pp. s. VII), which at once separates into two, a dor- 

 sal and a ventral. The two portions pass through a com- 

 mon foramen in the opercular bone. The ventral one 

 contains only coarse lateralis fibres and supplies the 

 penultimate (6th) canal organ of the opercular canal 

 {op. s. VII. i). In some cases it has a separate origin 

 from the truncus. 



The dorsal portion contains coarse and fine fibres. The 

 former, comprising about four-fifths of the area of the 

 cross- section of the nerve, are lateralis fibres; the latter 

 are derived almost exclusively from the general cutaneous 

 component before it has yet fused with the truncus. 

 Upon reaching the preopercular bone about three-fourths 

 of the coarse fibres are drawn off {op. s. VII. 2), enter a 

 foramen in that bone and supply the last (7th) canal organ 

 of the opercular canal. The remaining coarse fibres and 

 all of the fine ones continue caudad as a compact round 

 bundle between the preopercular bone and the ventral tip 

 of the hyomandibular. 



