GANGLIA AND NERVES OF SQUALUS 39 
sembles a general cutaneous nerve but the absence of any iso- 
lated general somatic ganglion argues against this view. It is 
more probable that it is a special visceral sensory nerve such as 
accompanies the ramus supratemporal IX in Menidia (Herrick, 
99). The visceral sensory ganglion on IX is so situated that 
fibers from that ganglion could readily enter the ramus supra- 
temporalis. From the point of origin of these two twigs the 
ramus supratemporalis curves dorsal and cephalad to end on the 
primordium of a lateral line organ (fig. 1, L.2) situated almost 
directly lateral to the proximal end of the ductus endolymphat- 
icus. 
19. RAMUS PHARYNGEUS AND RAMUS PRETREMATICUS Ix 
These two rami arise together as one nerve from the middle 
of the anterior border of the ganglion petrosum. The first 
twigs to be given off are the pretrematic rami (figs. 1 and 6, 
R.Pr.IX) which curve caudad and end on the epithelium of the 
gill bar. The second ramus or ramus pharyngeus (figs. 1 and 6, 
R.Ph.IX) turns ventral and mesial and after pursuing a much 
longer course comes into direct contact with the endoderm of the 
roof of the pharynx. All these rami are evidently visceral 
sensory. 
20. TRUNCUS GLOSSOPHARYNGEUS 
The truncus glossopharyngeus (figs. 1 and 7, R.PO.LX) arises 
from the distal end of the ganglion petrosum and is a combined 
sensory and motor root containing visceral sensory and visceral 
motor fibers so closely combined that they cannot be distin- 
guished. This nerve runs ventral and slightly caudad to the 
level of the floor of the pharynx. The first twig given off is 
sensory, arises quite close to the ganglion and runs to the endo- 
derm of the gill bar. The third twig (fig. 1, Mo.1) is motor 
entering the primordium of the branchial musculature as do all 
the motor twigs of this nerve. The second, fourth and fifth 
(figs. 1, S.2, 3 and 4) are sensory and run to the epithelium of the 
gill bar. The sixth twig (fig. 1, Mo.2) seems to be motor, as 
does also the seventh and terminal twig. However, the muscle 
