346 PROCEEDINGS OF THE CANADIAN INSTITUTE. 
The ventral muscles partly represent the ventral portions of the 
constrictors. Certain of them retain their original transverse direc- 
tion as the transv. vent. and the obliqui vent. The hyobranchiales, 
however, I feel disposed to consider as comparable to the ventral 
musculature of the trunk, in which case they must be considered as 
retaining for the greater part their original direction, the lateral 
portions merging into the constrictor type. A reason for this sup- 
position is the explanation it affords for the dissimilarities between 
these muscles in various forms, and for the very evident relation 
which exists between the obliqgui vent. and the slips from the 
hyobranch. As these points have already been treated of in connec- 
tion with the description of the latter muscles, it will not be neces- 
sary to repeat them here. 
The absence of any similar longitudinal muscles in the preceding 
arches points to the opposite view, but owing to the great changes 
which these have undergone, they may have disappeared by a con- 
tinuation of the process by which the intermandib. has become so 
much reduced. There is a possibility that the geniohyoid may repre- 
sent this ventral musculature, but I am rather inclined to refer it to 
the constrictor series. 
With regard to the musculature of the head it may be concluded 
that, in the theoretical ancestral type of the Te/eostei, it consisted of 
two portions, a dorsal greater one, constrictor in us nature, and a 
ventral smaller one, the fibres of which retained their original longi- 
tudinal direction. 
The Trunk Muscles.—The hyopectoralis by its innervation belongs 
to the first, or rather to the first and second spinal segments, and is 
referable to the longitudinal ventral portion of those segments. This 
being the case its attachment to the hyoid is rather peculiar. One 
would expect the musculature of the first spinal segment to be 
attached anteriorly to the posterior surface of the last arch or 
myocomma of the cranium. Between the hyoid and the first spinal 
segment there are five arches, to the most posterior of which one 
would expect to find the hyopectoralis attached, or if it were con- 
tinued further forward one would expect to find its anterior portions 
supplied by branches from the trunc. branch. vagi. This does not 
seem to be the case here, nor does Vetter describe any such arrange- 
ment in the forms he investigated. Probably along with the 
increased development of the hyoid apparatus, and the greater or 
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