270 



ALUS. [Vol. XVIII. 



from the hind edge of the fascia on the inner surface of A co, and 

 it Hes, throughout its entire course, dorsal to what seems to be 

 the slightly developed ligamentum mandibulo-hyoideum. In Aiiiia 

 the corresponding nerve runs downward postero-external to the 

 latter ligament, that is in a position relative to the ligament ex- 

 actly the opposite of that in which it lies in Scomber. The nerve 

 in Scomber must accordingly have traversed the ligament, if the 

 ligaments in the two fishes are homologous structures, which 

 seems, as already stated, doubtful. The nerve in Scomber then 

 runs forward, ventral to Meckel's cartilage, lying mesial to the 

 articular and dentary, and lateral to the mandibular part of the 

 adductor. It here passes lateral to the ligaments that are con- 

 nected with the fascia that lines the mesial surface of Aco, but 

 mesial to those tendons of AoA^ that have their insertions on or 

 near the hind end of Meckel's cartilage. Beyond this point it 

 accompanies, or anastomoses more or less completely with, that 

 large branch of the ramus maxillaris inferior trigemini, that I 

 have designated as r. gh. Before reaching the ventral surface of 

 Meckel's cartilage branches are sent from the nerve to organs 

 5 and 4 of the mandibular lateral canal, and then, further for- 

 ward, branches to organs 3, 2 and i of the same canal. 



The Ramus Mandibularis Internus Facialis (mif), after 

 leaving the truncus mandibularis, runs downward and forward, 

 and passing between the anterior edge of the symplectic and the 

 adjoining edge of the quadrate reaches the inner surface of the 

 latter bone. There it joins the mandibularis externus, and runs 

 forward into the mandible, lying parallel to and immediately dorsal 

 to the externus, but in no way connected with it. As it reaches 

 the hind end of Meckel's cartilage it turns slightly upward, mesial 

 to that cartilage, but it lies throughout its entire course either 

 imbedded in or lateral to the fibers of Aco. Anteriorly it either 

 anastomoses with the terminal portion of the maxillaris inferior 

 trigemini, or with a branch of that nerve, as already stated. The 

 main nerve, after the anastomosis, continues forward and is lost 

 in the tissues toward the symphysis of the mandibles. The 

 nerve thus dififers from the nerve in Amia, in that it lies in, or 

 lateral to, Aco, instead of ventral to that muscle. As already 

 stated, it must certainly be the chorda tympani of the animal, 



