156 J. B. Johnston 
branches are distributed to the skin of the upper lip. No neuro- 
masts are found here. 
Two peeculiarities of the ramus maxillaris are to be noticed in 
passing. The first is that several small branches from its chief 
inner branch seem to innervate pharyngeal muscles, and that the 
greater part of this inner branch goes to the muscle of the buceal 
funnel. The second is that the floor of the mouth and tongue are 
innervated also by a mesial branch of the maxillaris. It would seem 
that a part of the muscles and a part of the sensory area usually 
supplied in other vertebrates by the ramus mandibularis are supplied 
in Petromyzon by the ramus which is called maxillaris. 
The profundus. As the trigeminus ganglion is traced forward 
from 324 numerous fibers are seen collecting on its mesial surface, 
next the eranium. At the level of the mandibular rami (312) these 
fibers form a well defined large bundle much flattened between the 
dorsal part of the ganglion and the eranium (Fig. 2). The ganglion 
thus far is the trigeminus ganglion proper. Now (311) cells appear 
dorsal to the apex of the trigeminus ganglion in connection with 
the mesial bundle; this is the profundus ganglion. It grows larger 
and all the fibers of the mesial bundle enter it. At the same time 
the bundle mentioned above, composed of neuromast and general 
cutaneous fibers, joins the profundus trunk (Fig. 1). At 298 a small 
twig is given off dorsally and supplies two pit organs on the top 
of the head (Fig. 1). The profundus ganglion extends forward mesial 
to the eye-ball. The retina appears first in section 294 and section 
273 passes through the middle of the optie tract as it emerges from 
the retina. Opposite this the profundus ganglion practically ends; 
a few cells are found farther forward. 
The profundus continues directly forward to 235 where it gives 
off a branch dorsally which turns forward and runs at the side of 
the olfaetory pit. It is HarscHer’s branch 3. Continuing forward, 
the nerve divides in front of 194 into several branches whose arrange- 
ment is not the same on the two sides. These branches spread late- 
rally and mesially and subdivide into numerous twigs to the skin. 
At 120 the first pit organ of the supra-orbital row appears direetiy 
over one ofthe main branches and all of the organs of the row are 
supplied by this one branch. There are nine organs in this row in 
this specimen. Although it is not possible to distinguish the neuro- 
mast component throughout the length of the profundus nerve, no 
one will doubt that this branch is composed of the. fibers derived 
