Nos. IAND2.] ANATOMY OF SCOMBER SCOMBER. 219 



surface of the corresponding clavicle. Certain bundles of its 

 fibers, however, arise from the mesial surface of the bone, and 

 certain of them, both on its outer and on its inner surfaces, are 

 continuous with the trunk muscles that lie immediately posterior 

 to them. Certain other tendons or muscle-bundles come from the 

 muscles of the ventral fin. The fibers of the muscle do not arise 

 directly from the clavicle, but from a tough membrane that covers 

 that bone. On the sternum they are inserted directly onto the 

 bone without the intervention of such a covering membrane. 



On the outer surface of each clavicle the surface of origin of 

 the corresponding stcrnohyoideus occupies the full width of the 

 bone from its ventral end upward and backward approxi- 

 mately to the level of the anterior edge of the pharyngo-clavi- 

 cularis externus. There the hind edge of the surface of 

 origin runs upward and forward, across the bone, to a point on 

 a level with or slightly above the hind edge of the pharyngo- 

 clavicularis externus. On the inner surface of the clavicle the 

 surface of origin is much less extensive, extending backward, in 

 its dorsal portion, to about the same level as on the outer surface 

 of the bone, but occupying, ventrally, a much less important por- 

 tion of the surface of the bone. The surface of insertion of the 

 muscle occupies the full width of the posterior portion of the lat- 

 eral surface of the sternum. The surface of insertion of the 

 sterno-clavicular ligament occupies only the extreme postero-dorsal 

 corner of the sternum, the ligaments running downward and back- 

 ward from there to the anterior ends of the clavicles. 



In young fishes the lateral fibers of the stcrnohyoideus are not 

 continuous with the fibers of the trunk muscles that lie posterior 

 to them, the fibers of the two muscles arising from, and being 

 separated by, a tendinous band that lies along and is attached to 

 this part of the postero-ventral edge of the clavicle. In old fishes, 

 as stated above, certain muscle bundles of the sterno-hyoideus pass 

 backward beyond this band and penetrate and have their insertion 

 in the trunk muscles. 



The muscle is always crossed by certain tendinous lines, and is 

 imperfectly separated into several parts or bundles. Two of these 

 somewhat separate bundles lie^ along the dorsal edge of the poste- 

 rior portion of the muscle, one arising from the lateral surface of 



