SKELETAL MUSCULATURE OF THE KING SALMON. 51 



thick triangular muscular mass of the adductors comes into view on the inner and the poste- 

 rior surface of the coracoid. 



ADDUCTOR PECTORALIS SUPERFICIAUS. 



This is a short thick muscle lying in the angle between the coracoid and the clavicle 

 and the base of the pectoral fin. It takes its origin from the posterior ventral surface 

 of the coracoid, and the spine on the superior margin of this bone, also from the thin 

 bony plate lying between the superior margin of the coracoid and the clavicle. The 

 muscle fibers converge into a broad tendon which is inserted into the posterior surface 

 of all the dorsal half-fin rays except the first five. When this muscle is reflected a 

 deeper muscle is exposed. 



ADDUCTOR PECTORALIS PROFUNDUS. 



This muscle arises from the dorsal margin of the extreme ventral portion of the 

 da\ncle and the surface included in the angle between this margin and the bony ridge 

 projecting on the side of the clavicle, also from the connective tissue septum joining 

 the clavicle and coracoid. and from the dorsal margin of the coracoid including the upper 

 surface of the median spine. The muscle is divided into two parts. Those fibers 

 arising in the angle between the anterior end of the coracoid and the clavicle form a 

 stout tendon inserted into the stout base of the marginal ray. The remaining fibers 

 converge to strong tendons inserted into the bases of the dorsal half rays of the pectoral 

 from the second to the last. 



Contractions of the profundus support the contractions of the superficial muscle 

 in throwing the fin back against the side of the body. 



INTERFILAMENTI PECTORALIS. 



When the skin is removed from the basal half of the ventral surface of the pectoral 

 fin there is exposed a series of very delicate muscle fibers running across the bases of 

 the fin rays. These fibers run from ray to ray, being arranged diagonally so that when 

 they contract they tend to close the rays. No fibers were observed on the dorsal surface. 



MUSCLES OF THE PELVIC GIRDLE. 



ABDUCTOR VENTRALIS SUPERFICIALIS. 



A slender slip of muscle, the abductor ventraUs superficialis, arises from the median 

 longitudinal septum of the pelvis beginning at the ventral border of the anterior end 

 of the ischium, also from the adjacent cutaneous fascias. It is surrounded by a strong 

 aponurosis continuous anteriorly with that into which the tendon of the protractor 

 ischii is partially inserted. 



The superficialis runs as a slender wedge of muscle to a strong tendinous inser- 

 tion into the tips of the ventral half rays of the ventral fin. A cross section of the 

 middle of the muscle presents a wedge-shaped surface, the base of the wedge in approxi- 

 mation to the skin, the surface shown in figure 8, and the side in contact with the median 

 (vertical) septum. 



