THE MYOLOGY OF POLYODON 141 
occur, presumably represent the deep and superficial muscles of 
the median fins, and so perhaps Polyodon is ‘simplified’ rather 
than ‘primitive’ in this respect. 
M. trapezius: figure 8, m.trp. 
The trapezius muscle arises (a) to a slight extent from the 
skull, (b) from the upper two-thirds of the supraclavicle, and 
(c) from the adjacent aponeurosis over the lateral muscle of the 
body: Ventrally the body of the muscle turns slightly ante- 
riorly and is inserted chiefly into the upper angle of the cartilage 
of the arch. Towards its insertion, however, it is somewhat 
tendinous and this tendinous portion is more or less a in 
the neighboring sheets of fascia. 
Innervation. This muscle is supplied by a long branch of the 
vagus nerve which enters it dorsally near the upper end of its 
insertion by crossing to it from the jugular vein which it has 
followed back. This innervation is rather unexpected, since in 
some forms, e.g., Ameiurus (MecMurrich ’84), apparently the same 
muscle is supplied by the first spinal nerve. The innervation 
found here suggests its homodydamy with the levator muscles 
of the gills and hyoid arch. 
Blood supply. The arteries of supply come from the coronary 
and the subclavian arteries, chiefly the latter. 
Action. Its action is to raise the pectoral girdle. 
Adductor of the pectoral fin: figure 8, m.adp. 
The fibers of this muscle have a rather extensive field of origin, 
but no intermuscular septa or other noticeable demarcations* 
warrant its being considered as more than one unit. The pos- 
terior and superficial fibers arise (a) from the anterior two-thirds 
of the posterior ramus of the coracoid cartilage along a groove 
on its ventral margin, and (b) from an aponeurotic sheet invest- 
ing the body of the muscle and binding it to the cartilage both 
laterally and medially. Anteriorly, some of these fibers are some- 
what tendinous, both at their origin and at their insertion. The 
fibers in the ‘center of the muscle take origin (a) from all sides of 
