190 JouRNAL OF COMPARATIVE NEUROLOGY. 
their respective termini in the skin. Upon emergence from its 
canal in the preopercular bone the hyomandibular trunk divides 
at once into the r. hyoideus and the r. mandibularis externus 
and the latter nerve turns at once by aright angle and runs 
cephalad along the outer face of the hyomandibular bone, from 
which, however, it is separated by a wing of the preoperculum. 
In this position, internal to the ventral edge of the m. adductor 
mandibulae, the nerve divides into two branches: the smaller 
one is external running cephalad close under the skin and may 
be termed the cutaneous branch of the r. mandibularis externus 
VII (cut. m. ex. VIT, on Fig. 1), while the larger branch enters 
the alveolar canal and supplies the organs of the mandibular 
canal in the way typical for the main r. mandib. ext. of other 
teleosts (r. man. ext.i VII, of Fig. 1). The latter branch ap- 
parently carries only lateral line fibers, while the former includes 
communis, and probably also general cutaneous fibers, as shown 
by their peripheral distribution. 
Before the separation of these two branches a lateral twig 
leaves the nerve for the last (eighth) organ of the operculo- 
mandibular canal and two or three smaller twigs for the skin 
adjacent, some of whose fibers were definitely traced into ter- 
minal buds. They doubtless also contain general cutaneous 
fibers for the same area, viz. the region of the caudal part of 
the preopercular bone. The few general cutaneous and com- 
munis fibers of the external mandibular nerve not thus distrib- 
uted go out for the most part with the earlier twigs of the 
cutaneous branch for the skin under and behind the eye. Some 
of these were definitely traced to terminal buds. The source 
of the nerve supply of the small pit organs of the same region 
was not determined, probably from these same twigs. 
The main external mandibular nerve, after supplying the 
seventh organ of the operculo-mandibular canal, passes down 
through a notch between the preoperculum and the hyomandib- 
ulare to the ventral side of these bones then, after a second 
ventrally directed bend, runs cephalad under the interoperculum 
and external to the quadrate. Upon entering the mandible this 
nerve takes up the usual position along the inner face of the 
