THE SHOULDER GIRDLE AND PECTORAL FIN OF FISHES. 
557 
(i) Superior (see fig. 15). 
The markedly oblique fibres which compose the lower part of the lateral body-wall 
pass into a tendinous sheet which is inserted into the lowermost part of the posterior 
face of the coraco-scapula. 
(ii) Inferior (see fig. 14). 
The ventral body-wall near its middle line passes anteriorly into a sheet of con- 
nective tissue which is inserted into the hinder border of the clavicles, forming the 
ventral wall of the pericardium. Laterally some of the fibres pass forwards, between 
the pericardial fascia and the coraco-scapula, and internal to the ventrally projecting 
process of the latter, to be inserted on the bases of the visceral arches. The last- 
named muscle mass will be described later under the heading claviculo-hyoideus. 
(3) The Anterior Muscles. 
A. Connections with the Skull. — The presence of a “ trapezius” muscle is denied 
by Gegenbaur and Vetter for Accipenser sturio. Meissner (63) describes such a 
muscle in A. nudiventris, A. stellatus, A. stenorhynchus, and Pseudoscaphirhynchus 
Kaufmani, and associates its presence with the increased mobility of the shoulder- 
girdle in these forms compared with that in A. sturio ; he even proposes on these 
grounds to reinstate the old generic name of Sturio for the latter species. Ostrotj- 
moff describes the development of a “ trapezius ” in A. giildenstadtii and A. ruthenus. 
I have shown the muscles of this area in A. rubicundus in fig. 15. It is also present 
in Poly don. 
Ostroumoff states that the development of the “trapezius” muscle, likewise its 
innervation (from the ramus accessorius of the vagus), leads to the conclusion that 
this muscle belongs to the dorsal suprabranchial section of the superficial constrictor, 
which is not severed into myomeres, and in the beginning of its development includes 
six myomeres representing the five gill pouches and the sixth rudimentary pouch. 
Its development pulls the shoulder girdle forwards against the gill apparatus. Thus 
the embryonic condition in the Chondrostei recalls vividly the adult condition in 
the Selachii. 
Meissner also shows that the trapezius is divided into two distinct portions, but 
does not name them. 
( a i) Protractor pectoralis anterior. Trapezius (pars), Meissner. 
Lies immediately beneath the skin. It takes origin on the skull just behind 
the retractor hyomandibularis, and is inserted on the scapula and in part also on 
the cleithrum. 
(< a ii) Protractor pectoralis posterior. Trapezius (pars), Meissner. 
A very small muscle, lying somewhat deeper and posterior to the foregoing, takes 
origin on the suprascapula and is inserted on the scapula. 
