MUSTELUS L^EVIS. 181 



tonioso coiiiplotoly, exactly as the branch r. g-lii of the maxil- 

 laris inferior trigemini and the ramus hyoideus facialis of 

 Amia do (3). The relations of the nerves to the muscles are 

 not exactly the same in Mustelus and Amia^ but the diifer- 

 ences are probably Jiot of morphological importance. 



The mesial one of the two branches sent forward alonp- the 

 external surface of the adductor by this ramus ad muse, inter- 

 mand. passed beyond the adductor on to the ventral surface 

 of the intermandibularis^ and there, at a certain point in my 

 sections, was lost while it still had a relatively large section. 

 Whether it penetrated the intermandibularis muscle, as the 

 main branch did, or not, could not be determined. The other 

 and lateral one of the tAvo branches continues forward beyond 

 the anterior edge of the adductor nmscle, approaching and 

 accompanying the main mandibularis nerve in the terminal 

 part of its course. 



The main ramus mandibularis, after giving off the large 

 branch above described, continues its forward and mesial 

 course, lying immediately dorso-lateral to the mandibularis 

 externus facialis, both nerves soon passing beyond the anterior 

 edge of the adductor muscle and reaching the ventral surface 

 of the mandibular cartilage, near its lateral edge. The ramus 

 mandibularis here lies directly lateral to the mandibularis 

 externus facialis. Somewhat mesial to the latter nerve, and 

 following an approximately parallel course, is the anterior 

 l)ranch of the ramus ad muse, intermand. just above 

 described. 



When the ramus mandibularis reaches the transverse level 

 of the hind end of the mandibular labial cartilage, a branch 

 is sent outward from it into the mandibular labial fold. The 

 main nerve then separates into three or four branches, all of 

 Avhich continue forward, and here, at first, lie along the ventral 

 surface of the mandibular labial cartilage. At the level of 

 the anterior end of that cartilage the nerve passes internal to 

 the mandibular group of ampullae, those ampullae here taking 

 up the larger part of the mandibularis externus facialis, a 

 small branch only continuing forward to supply the anterior 



