26o ALUS. [Vol. XVIII. 



short part of the nerve that hes exposed on the outer surface of 

 the adductor mandibulse muscle, between its superficial and deeper 

 divisions, near their distal ends. It turns downward and back- 

 ward external to the deeper division of the adductor, and then 

 along the hind edge of the mandible. Somewhat below the ventral 

 edge of the adductor it enters a small canal in the articular, turns 

 sharply forward, and traversing the bone issues at its anterior 

 edge. There, lying in the tissues between the articular and den- 

 tary, it turns downward toward the lower edge of the mandible, 

 passing, in its course, mesial to the mandibular lateral canal but 

 lateral to the mandibularis externus and internus facialis. It thus 

 lies between the mandibular lateral canal and the nerve that in- 

 nervates the organs of that canal, and hence must, if it arise by 

 being split off from the ectoderm, have been so split off after the 

 mandibularis externus facialis had so arisen, and before the man- 

 dibular canal had been enclosed. 



From this fourth branch of the maxillaris inferior two princi- 

 pal branches are given off. The first one turns upward and for- 

 ward along the hind edge of the mandible, runs internal to the 

 dorsal portion of the distal end of the superficial division of the 

 adductor, and reaches the dorsal portion of the coronoid process 

 of the articular. There it turns sharply forward, mesial to that 

 process, and, running directly forward, is lost in the lining mem- 

 branes of the inner surface of the mandible. It is accordingly, in 

 its ultimate distribution, the homologue of the mandibularis inter- 

 nus trigemini of my descriptions of Aniia, but it runs, in Scomber, 

 ventral and internal to the superficial division only of the adductor 

 mandibulse, and not, as in Ainia, ventral and internal to both divi- 

 sions of that muscle. The second branch enters a small canal in 

 the articular, dorsal to and similar to the one traversed by the 

 terminal portion of the main branch, and running forward and 

 slightly upward issues from the bone near its anterior edge and 

 is distributed to tissues there. In one specimen another branch 

 of the nerve was found which seemed to be running toward the 

 inner surface of the ventral end of the preoperculum, but it was 

 lost, in the dissection, before it reached that bone. 



This fourth branch of the maxillaris inferior of Scomber thus 

 corresponds closely to the fourth branch of the same nerve in 



