Herrick, Nerves of Silurotd Fishes. 189 
of the outer skin, chiefly in the region of the lower end of the 
preopercular bone. 
The motor branches belonging to the deep opercular nerves 
are given off from the truncus immediately distal to the fora- 
men of exit and then no other branches are given off until the 
trunk divides into the r. hyoideus and the r. mandibularis ex- 
ternus VII. The nerves corresponding to the r. opercularis 
superficialis VII of many other fishes seem not to be repre- 
sented in Ameiurus. 
8. Ramus hyotdeus. 
This nerve separates from the external mandibular at the 
outer edge of the hyomandibular bone and apparently receives 
from the trunk motor and general cutaneous fibers only. It 
descends at once into the ,branchiostegal apparatus, whose skin 
and muscles are innervated by it. The skin of the outer sur- 
face of the branchiostegal membrane bears occasional terminal 
buds and small pit organs which may be supplied from this 
nerve, though their fibers could not be traced. 
The more fleshy inferior part of the m. hyohyoideus lies 
close under the m. geniohyoideus and between these muscles 
some filaments of the r. hyoideus effect minute terminal anas- 
tomoses with the motor trigeminal fibers for the latter muscle, 
similar to what Axis described for Amia ('97, p, 613) and I 
have described for Gadus (’00, p. 278). The sections leave no 
room for doubt, however, that no appreciable portion of the 
geniohyoideus is supplied from the facialis and WRiGuHrT is evi- 
dently in error when he gives the innervation of this muscle 
and of the intermandibularis from the facialis (84a, p. 369). 
The innervation of these muscles in Silurus is given by JuGE 
(99, p. 28, 29, 32) as I have here described. 
9. Ramus mandibulans externus facials. 
After separating from the r. hyoideus this nerve carries 
both coarse and fine fibers. The former comprise all of the 
lateralis fibers of the hyomandibular trunk, the latter are gen- 
eral cutaneous and communis fibers so intimately mingled that 
it is not possible to distinguish them until they separate for 
