146 EDWARD PHELPS ALLIS, JR. 



lower jaw. The ramus internus is composed entirely of com- 

 munis fibers, and contains most, if not all, of those fibers of the 

 nerve. 



The ramus hyoideus facialis is thus either simply the ramus 

 posttrematicus posticus of the nervus facialis, or that ramus 

 plus the ramus medius; the ramus mandibularis externus is 

 either the ramus posttrematicus anticus alone, or that nerve 

 plus the ramus medius, and the ramus mandibularis internus is 

 the ramus posttrematicus internus. 



The ramus palatinus facialis separates while in the cranial 

 cavity into two parts, which issue from the cranial cavity by 

 separate foramina. The posterior branch is the smaller of the 

 tw^o, and, as already stated, anastomoses completely with a 

 branch of the ramus pharyngeus glossopharyngei to form a com- 

 municating branch between the ganglia of the nervi glosso- 

 pharyngeus and facialis which apparently corresponds to the 

 Jacobson's anastomosis of the Teleostei. The anterior and 

 larger portion of the palatinus issues through an independent 

 foramen and forms the ramus palatinus properly so called. 

 Running forward, it sends a small branch outward over the 

 dorsomesial edge of the palatoquadrate to join and fuse with 

 the ramus mandibularis trigemini, and two or three branches 

 downward internal to the palatoquadrate; the former branch 

 being the ramus pretrematicus externus facialis and the others, 

 together, forming the ramus pretrematicus internus, usually 

 called, in current descriptions of other fishes, the ramus pala- 

 tinus posterior. The remainder of the ramus palatinus is then 

 the ramus pharyngeus facialis and runs forward in the roof of 

 the buccal cavity. 



The nervus facialis thus has all the branches tj^pical of the 

 more posterior nerves, but it differs from them and also from 

 the nervus trigeminus in that its ramus posttrematicus contains 

 lateralis fibers. These fibers must therefore be either pre- 

 existing fibers that have undergone both change of function and 

 change of central origin, or fibers that have invaded this arch, 

 as the nervus lineae lateralis invades the body of the fish, by 

 following a patch of sensory tissue which has given rise both to 



