RAMUS MANDIBULARIS VII. 145 



which it turns dorsad around the base of a scale to a 

 naked sense organ {0.6) lying on the outer face of the 

 scale and just overlapped by the free edge of the next 

 dorsal scale. The larger part of this first ramulus con- 

 tinues ventrally along the outer face of the preopercular 

 bone to the opercular canal. It enters the bony canal and 

 just dorsally of the membraneous canal it divides, a minute 

 twig turning cephalad, the larger portion caudad. The 

 latter supplies four naked organs on the outer skin cover- 

 ing the most caudal part of the horizontal limb of the 

 opercular canal and the base of the fourth pore of that 

 canal. The former supplies a single similar but larger 

 organ on the base of the third pore. The fibres of this 

 ventral part stain very intensely, like lateralis fibres, 

 though they are of small size. 



On the opposite side of the specimen figured this first 

 branch pursues a course similar to that just described 

 except that all of its fibres pass through from the mesal to 

 the lateral face of the m. adductor mandibulae before it 

 divides into its dorsal and ventral ramuli. The ventral 

 ramulus then passes down the outer face of the muscle 

 instead of its inner face to reach the opercular canal. 

 Here it supplies four naked organs with its caudal twig, 

 but the cephalic twig, after supplying a naked organ just 

 caudad of the third opercular pore, continues cephalad, 

 receives a considerable addition from the second branch 

 of the r. mandibularis VII just before the latter enters the 

 fourth opercular canal organ and then supplies a large 

 sense organ lying just cephalad of the third opercular pore. 



All of the naked organs supplied by this branch, as well 

 as similar ones farther cephalad, to be described immedi- 

 ately, are of the same nature as the similar but larger 

 organs supplied by the r. opercularis superficialis and I 

 homologize them with the pit-lines of ganoids. They 

 correspond, doubtless, to the similar lines mentioned by 



