514 ALLIS. [VoL. II. 
this most posterior of the dorsal twigs of the seventh in Mus- 
telus as homologous with the ramus oticus in Ganoids and Tel- 
eosts (No. 20, p. 490). 
The ophthalmic branch of the facial is closely associated 
throughout most of its course with the ophthalmic branch of the 
trigeminal, but there is apparently no interchange of fibres be- 
tween them; and in the youngest specimens examined, the two 
nerves were wholly separate, although lying close together. 
The R. buccalis facialis supplies the first thirteen organs of 
the infra-orbital line, and the R. oticus facialis the next three, 
making sixteen organs in all of this line supplied by the facial, 
or all those in front of the line of the opercular canal. The 
remaining organs of the infra-orbital line are innervated by the 
glossopharyngeal and vagus. 
The sixteen infra-orbital organs supplied by the facial are 
separated by their innervation into four distinct groups. The 
first four, all belonging to the anterior commissure, form the 
first of these groups. They are supplied regularly by separate, 
consecutive branches given off from the anterior portion of the 
R. buccalis, which ends in the first one of them. The next six 
organs, from 5 to 10 inclusive, form the second group of the 
line, and they are also supplied by separate branches of the 
R. buccalis; but the branches to organs 5 and 6 are given off 
close together, the one to No. 6 passing outward behind the fifth 
division of the M. levator arcus palatini (McMurrich, No. 10, 
p. 122), and the other to No. 5, internal to, and in front of, 
this muscle. The origin of these two nerves close together 
from the main R. buccalis is easily explained by supposing the 
first four organs of the canal in Amia to have belonged to a 
line of pit organs in some earlier form. As the separate organs 
of such a line are always much smaller than those found in the 
canals, and as the nerve that supplies a whole line of them, 
where still found in Amia, is no larger, or not so large, as the 
branch sent to a single canal organ, the main part of the ramus 
buccalis would, in such an earlier form, have ended in the termi- 
nal organ of the canal; that is, in organ 5 of the line in Amia ; 
and what is the anterior part of the nerve in Amia would, in 
that form, have been simply a smaller branch sent to the organs 
of the pit line, and given off beyond and rather close to the 
branch to organ 6, just as a similar branch, destined to supply 
