2 28 ALUS. [Vol. XVIII. 



the superficial muscle has, but it acts less as a depressor and more 

 as an abductor. It is, in McMurrich's nomenclature, the abductor 

 profundus of the fin. 



The third lateral muscle (Le) is a long and somewhat S-shaped 

 one. It arises from the bottom of the grooved surface of the 

 clavicle, its surface of origin extending from the ventral end of 

 the bone nearly to the dorsal end of the grooved portion, and 

 occupying parts of both walls of the groove. Its ventral end is 

 exposed ventral to the ventral edge of the superficial abductor 

 muscle. Its fibers converge strongly and are inserted on a long 

 tendinous aponeurosis, which begins almost at the ventral end of 

 the muscle and lies nearer its posterior than its anterior edge. 

 Distally the muscle becomes entirely tendinous and is inserted on 

 the anterior surface of the shaft of the mesial one of the two 

 bones that together form the first dorsal ray of the fin, the sur- 

 face of insertion lying immediately distal to the proximal end of 

 the half ray. It is, accordingly, the levator muscle of the fin ; 

 that is, it raises the dorsal edge of the fin, and spreads the rays 

 one from the other. Near its distal end it traverses a tendinous 

 formation that arises from the curved line that marks the dorsal 

 continuation of the grooved part of the clavicle. The fibers of 

 this formation converge toward the proximal end of the dorsal 

 edge of the fin, and are inserted on the dermal rays, on the two 

 abductor muscles, and on the adjoining parts of the primary 

 girdle. The tendon is traversed by a well formed, closed canal, 

 which lodges the distal end of the levator muscle, and, holding 

 it, as in a pulley, greatly adds to its efficiency. 



The nerve that supplies these three lateral muscles issues 

 through the foramen in the scapulare, sends one branch at once 

 to the dermal parts of the fin and another to the S-shaped levator 

 muscle, and then, running downward between the two abductor 

 muscles, sends branches to them also. 



The ventral ends of the lateral muscles lie internal to the an- 

 terior part of the trunk muscles, which muscles here have their 

 insertion on the clavicle superficial to the muscles of the fin. 



The mesial muscles of the fin, like the lateral muscles, are repre- 

 sented by three muscles, one of which is a superficial muscle and 

 the other two deeper ones. The superficial muscle, and the dorsal . 



