392 HOWARD AYERS 
carried the nerve with it. After its curve around the anterior 
end of the auditory capsule it runs ventrad and laterad, keeping 
close for a time to the hyoid arch, and then it sweeps forward, 
in a curve for a distance, on the surface of the muscles just above 
the lateral border of the hyoidean plate to reach its final termina- 
tion in the nerve veil about the fourth tentacle. In its course 
it sends branches to several hyoidean muscles. As it crosses 
the copulo-palatinus it sends a small branch dorsad into a small 
muscle (fig. 36, VIZ m.) about an eighth of an inch long and thin- 
ner than tissue-paper. This muscle lies closely applied to the 
surface of the copulo-palatinus. Perhaps it is a vestigial muscle. 
Its function is not apparent. I have found several structures 
in Bdellostoma which are as non-conformist as this minute 
muscle and will consider them in a later contribution. 
This fifth segmental nerve, the most posterior of the group, 
does not reach any part of the distal jaw apparatus other than 
the fourth tentacle and its connections are mainly to the jaw 
supporting apparatus. It is thus distinctively a hyoidean nerve. 
It also does not innervate any of the muscles which move the 
dentigerous jaw nor the mucosa in any part as far as my observa- 
tions go. In this it differs from the homologue in fishes higher up. 
It is postvelar and in Bdellostoma postmandibular. It has less 
to do with the structures of the jaw bar than either the ophthal- 
mic, maxillary, or mandibular nerves. Like the nasalis at the 
anterior end of the series which has specialized in the service of 
the olfactory apparatus, the facial at the posterior end of the 
series has specialized in the service of the hyoidean apparatus. 
It takes part in the formation of the nerve veil, sending its con- 
tributions into the net near the fourth tentacle. The connection 
with the ophthalmicus superficialis noted by P. Fiirbringer is 
one of these net connections, and it is impossible, as I find it, to 
yet determine what nerve elements the facial connects with, 
as not only the ophthalmicus superficialis, but also the other 
nerves of the jaw apparatus take part in the net building. The 
nearest trunk to the facial in this locality is what Miss Worthing- 
ton has called the nerve VIII a, and Allis the buccalis. This 
nerve runs out below the eye, 1.e., posterior to it and conse- 
