RAMUS OPERCULARIS SUPERFICIALIS VII. I4I 



The r. opercularis superficialis VII and its principal 

 branches can easily be followed, and it is seen to supply 

 four naked sense organs along the lower margin of the 

 operculum (o.i to o.^z). They are large and flat and lie 

 upon or below the lowest row of opercular scales in a line 

 which is the direct continuation caudad of the horizontal 

 limb of the opercular canal, this line passing through the 

 fourth opercular pore. The number found was uniformly 

 four, except in one case, where the first one seemed to be 

 double. The arrangement varies somewhat in different 

 specimens, but never deviates greatly from that figured. 

 The two organs found in the sections and figured on Fig. 

 3 are probably numbers 3 and 4 of the series. The naked 

 organs along the outer surface of the opercular canal, to 

 be described presently, could also be distinctly seen. 

 Their number and arrangement vary greatly in different 

 specimens, but they are always smaller than the four 

 organs supplied by the r. opercularis and when examined 

 in the unstained specimens with a low power look like 

 little discs with a brilliant highly refracting centre. 



The organ lying behind the sixth opercular pore was 

 seen in a few instances. It may be followed by other 

 organs behind, as suggested above, for the preparations 

 here are opaque and confused by reason of the thick origin 

 of the underlying m. dilator operculi. 



Regarding the morphology of these five or six naked 

 opercular organs, I think there is but one conclusion pos- 

 sible. That they belong to the lateral line rather than 

 to the communis system is shown by their innervation. 

 See further. Section 2, III. 



Stannius makes no mention whatever of the r. opercu- 

 laris superficialis. That it is not contained in his r. oper- 

 cularis VII is shown by the fact that he correctly regards 

 that nerve as exclusively motor; z. e., his r. opercularis 

 is our r. opercularis profundus only. 



After giving off the r. opercularis superficialis VII, the 

 truncus hyomandibularis continues directly ventrad in a 

 canal of the hyomandibular bone until the ventral edge of 



