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 obliqui 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 i-ather 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 Teleostei, it consisted of 

 two portions, a dorsal greater one, constrictor in its 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 Yetter describe any such arrange- 

 ment in the forms he investigated. Probably along with the 

 increased development of the hyoid apparatus, and the greater or 



