NoRRis, Nerves of Amphnima. 551 



inferior), and to m. subarcualis obliquus (m. constrictor arcuum 

 branchiarum superior), and continues anteriorly to innervate the 

 m. ceratohyoideus internus. It also sends communis branches 

 to the ventral wall of the pharynx. The third branchial posttre- 

 matic according to Druner has no motor fibers in its ventral 

 portion, although in describing the mm. subarcuales he says they 

 receive branches from the second and third branchial nerves. I 

 find that the greater part of the ventral portion of the third 

 branchial posttrematic is of communis fibers distributed, as 

 Druner says, to the ventral pharynx wall at the sides of the 

 larynx; but I also find a small motor branch given off to m. sub- 

 arcualis rectus 3, and in one instance I have traced fibers to the m. 

 subarcualis obliquus. Between the posttrematic divisions of the 

 second and third branchial nerves and the ramus intestinalis 

 recurrens X there occur anastomoses such that it is difficult to 

 distinguish the source of some of the fibers innervating the subar- 

 cual muscles. 



/. The rami laterales X. — ^From the posterior end of the IX-X 

 ganglion there pass out two large nerve trunks. The dorsal of 

 these is composed solely of lateralis fibers, and soon divides form- 

 ing a smaller dorsal r. lateralis dorsalis supplying the neuromasts 

 of the dorsal series of the trunk of the body, and a larger ventral r. 

 lateralis medius supplying the median series of neuromasts of the 

 trunk. The remaining lateralis component of the vagal group 

 will be described in the following section. 



g. The ramus tntestino-accessorius X. — The second great trunk 

 passing posteriorly from the IX-X ganglion is the r. intestino- 

 accessorius, composed of lateralis, communis and motor fibers. 

 The communis and motor fibers have a very diverse distribution. 

 A short distance posterior to the ganglion there leaves the main 

 trunk a small nerve of communis and motor fibers, that in part 

 represents fourth and fifth branchial nerves. It sends motor 

 fibers to mm. levator arcus branchialis 4, trapezius and dorso- 

 laryngeus. The branches to the trapezius and dorso-laryngeus 

 muscles may arise separately from the main int. -ace. trunk. 

 After giving off" fibers to the m. lev. arc. br. 4, the nerve, now of 

 communis fibers only, passes near the dorsal ends of the third and 

 fourth branchial arches and there divides, one branch running 

 along the anterior median border of the third branchial arch, 

 and evidently forming a fourth ramus pretrematicus {prt. X. 5), 



