282 ALUS. [Vol. XVIII. 



and downward, passes dorsal to the interarcualis dorsalis of the 

 first and second arches, and reaches the dorsal surface of the first 

 epibranchial immediately distal to the suprapharyngeal process 

 of that element, thus lying posterior to the external levator of the 

 first arch. From there the nerve runs distally, the full length 

 of the arch, as a separate and independent nerve, lying always 

 postero-mesial to the artery of the arch. It gives off in its course 

 numerous branches, none of which fuse with the branches of the 

 posttrematic branch of the glossopharyngeus. Distally, at the 

 point where the afferent artery of the arch reaches the ventral 

 surface of the hypobranchial, the delicate ends of the nerve 

 turned mesially, toward the basal line, and were lost. 



From the pretrematic nerve, at and close to the point where it 

 separates from the pharyngeal branch, several small branches are 

 given off. In the one specimen in which they were especially 

 examined, they united with each other and with a single branch 

 from the posttrematic part of the nervus, and formed a sort of 

 plexus, the branches of which were all distributed along the dor- 

 sal surface of the interarcualis dorsalis of the first and second 

 arches, certain of them entering that muscle and undoubtedly in- 

 nervating it. 



The posttrematic branch of the nervus runs downward, back- 

 ward and laterally, and passing ventro-mesial to the anterior pro- 

 longation of the efferent artery of the arch reaches the dorsal 

 surface of the second arch along the surface of insertion of 

 the interarcualis dorsalis that connects that arch with the first 

 one. It then continues distally along the arch, lying always 

 toward the antero-lateral edge of the arch, and antero-lateral to 

 the arteries of the arch. Toward the distal end of the hypo- 

 branchial of the arch, the main nerve, or one of its terminal 

 branches, perforated that element and appeared on its antero- 

 lateral surface. There it turned upward and broke up into deli- 

 cate terminal branches which ran forward and backward along 

 the lateral surface of the basal line. 



The posttrematic nerve gives off, in its course, several branches. 

 The first branch is given off not far from the ganglion of the 

 nerve, and innervates the posterior division of the internal levator 

 of the arches. The next branch is given off about where the 



