910 THE AMERICAN NATURALIST. (VoL. XXXIX. 
muscle extends through only the posterior three fourths of this. 
The fibers, which become thinner posteriorly, run obliquely down- 
ward and backward, the majority being inserted on the anterior 
edge of the pectoral girdle, while the more anterior fibers turn 
directly downward and are inserted on the dorsal edge of the 
last branchial arch. At intervals tendinous strands of the dorsal 



n 
FiG. 10.— Ventral vi f Acanthias showi 

g th branchiales. CBr, coraco-branchiales ; 
Csd 2-6, constrictores superiores dorsales; Znźór, interbranchialis. 
constrictors (Fig. 11, Csd) as already described, pass through this 
muscle. The function of the trapezius is to raise the girdle and 
draw it forward. 
Rata. 
A trapezius has not been described in the skates but there 
occurs here a muscle (Fig. 6, 77) which in its attachments and 
