142 NERVE COMPONENTS OF BONY FISHES. 



the bone is reached. Here it divides into the r. hyoideus 

 and the larger r. mandibularis. The latter turns abruptly 

 cephalad, leaving the canal and running along the outer 

 surface of the bone to its cephalic tip. 



J. — The Ramus Hyoideus VII. 



The ramus hyoideus (/^J'.) runs ventrad and caudad. 

 Its first branch (Jiy. i) separates at once and might be con- 

 sidered a separate nerve. It contains only coarse fibres, 

 enters the lateral line canal of the preoperculum and 

 supplies the fifth opercular canal organ. 



The remaining and larger portion of the r. hyoideus 

 contains coarse and fine fibres and descends along the 

 inner face of the preopercular bone, and lower down along 

 the inner side of the interopercular bone, nearly to the 

 first (most dorsal) branchiostegal ray. Here it divides 

 into two approximately equal divisions, each with both 

 coarse and fine fibres (560). Of these one, which may be 

 regarded as the main ramus, turns slightly cephalad, the 

 other {/ly. 2) continues caudad and ventrad and will first 

 be described. It follows dorsally a big blood vessel run- 

 ning along the inner face of the interopercular bone, 

 giving off at once a sm.all twig which later rejoins the 

 main trunk, then several smaller branchlets which could 

 not be traced, and at 610 a slightly larger branch of fine 

 fibres with a few coarse ones, which passes directly dor- 

 sally between the subopercular and interopercular bones 

 to emerge upon the skin dorsad of the latter bone. It dis- 

 tributes to the skin covering the cephalic half of the sub- 

 operculum. The remainder of this nerve breaks up in 

 the branchiostegal membrane, which it innervates. 



The cephalic or main division of the r. hyoideus passes 

 ventrad in two branches, each with coarse and fine fibres. 



