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an independent branch arises for the oblique dorsal musculature of 
the gill arches, which is, however, in part supplied by a branch of 
tr. branch. IV. . 
Directly behind the most posterior of the levatores branchiarum, 
and separated by it from the nerves in front, the ramus lateralis 
vagi originates from its subdivision of the ganglionic complex. It is 
at first parallel in its direction to the transverse portion of the 
supraclavicle, but afterwards crosses it (Fig. 14, Pl. IV.) and becomes 
superficial over the air-bladder and behind the ascending process of 
the supraclavicle. Here it gives off its branch in the course of the 
accessory lateral line which can be traced along the line of junction 
of the ventral and lateral musculature as far as the line of attach- 
ment of the superficial muscles of the anal fin (Fig. 6, Pi. L.), while 
the stem is continued backwards in the line between the dorsal and 
ventral parts of the lateral musculature. Whether as Mayser asserts 
for Cyprinus the fibres of the ramus lateralis are those which I have 
named radix acusticus vagi J., | have been unable to demonstrate in 
Amiurus, but the fact that the mucous canals of the head are sup- 
plied by fibres from the tuberculum acusticum would lead one to con- 
clude that the same is true of those of the trunk. 
370 PROCEEDINGS OF THE CANADIAN INSTITUTE. 
SPINAL NERVES. 
Of these there are forty-one pairs, of which the first emerge 
through the exoccipitals, the more anterior of those which follow 
by separate apertures for the dorsal and ventral roots through the 
arches of the corresponding vertebre (e. g., the 7th pair through the 
arch of the 6th vertebra) and the more posterior through notches on 
the posterior borders of the arches, which are closed into foramina by 
articulating processes from the succeeding vertebre. 
The second and third spinal nerves have no foramina, for owing to 
the modification of the anterior vertebrz in connection with the 
auditory organ, the wall of the neural canal is membranous in that 
region. The dorsal and ventral root of the second are further apart 
from each other than those of the third, but they emerge very close 
to these, much closer than their points of origin from the spinal cord 
would indicate. (Fig. 8, Pl. IV., and Figs. 2and 3, Pl. VI.) This 
backward position of the points of emergence of the roots of the 
second nerve is to be explained by the formation of that diverticulum 
of the dura mater known as the atrium sinus imparis and the alteration 
