696 ALLIS. [Vou. XII. 
obliquus dorsalis. From the main nerve, near its base, in one 
specimen (Fig. 59), a long and delicate branch was sent to the 
fifth levator. In another specimen, the one used for illustra- 
tion, this nerve arose from the main truncus of the nerve, or 
from the united trunks of the third and fourth vagus. The 
branch that goes to the levator muscle innervates that muscle, 
and then the adductor of the fourth arch, passing to the latter 
muscle over the outer and posterior end of the arch. The 
main nerve, after giving off these branches, passes under and 
anterior to the levator of the fourth arch, and reaches the upper 
surface of that arch beyond the muscle. There it is not joined, 
as the corresponding branch on the other arches is, by pretre- 
matic branches of the next following vagus nerve. It, however 
itself, separates, on the ventral aspect of the arch, into two, 
three, or four branches, the smaller ones of which lie along the 
anterior and posterior edges of the arch, the main central 
portion running forward and inward onto the ventral surface of 
the obliquus ventralis of the arch. There it breaks up into 
several branches which enter and supply the obliquus of the 
arch, the two divisions of the so-called obliquus of the fifth 
arch, and the several divisions of the transversus ventralis 
anterior. Other branches are doubtless distributed to the 
cutaneous tissues between the fourth and fifth arches, though 
this was not definitely traced. 
The fourth vagus ganglion (gv4) is a large one, either well 
rounded or somewhat elongated, and from it arise two nerves. 
The outer or anterior of these nerves is apparently the truncus 
pharyngeus inferior of Stannius, the other the united truncus 
pharyngeus superior and truncus intestinalis. The truncus 
pharyngeus inferior separates at once into two branches, the 
outer or anterior of which is, from its distribution to the 
muscles of the fifth arch, the ramus branchialis anterior of 
that arch, or the ramus posttrematicus n. vagi quarti (rv). 
The other branch is the ramus pharyngeus inferior of Stan- 
nius, but as it is in part, at least, a motor nerve, it cannot 
be compared with the pharyngeal branches of the other vagus 
nerves. The two nerves run backward and downward, close 
together, to the hind end of the branchial arches, lying 

