Nos. IAXD_^] AX ATOMY OF SCOMBER SCOMBER. 217 



branch of the posttrematic branch of the fourth vagus also comes 

 into relations with it and may in part or wholly innervate it. 



The pharyngo-clavicularis externus (Pec) arises in a slight de- 

 pression on the antero-lateral surface of the antero-lateral plate 

 of the clavicle, approximately at the ventral third or quarter of 

 that bone. It lies, at its origin, internal to the dorsal edge of that 

 part of the sterno-hyoideus of its side of the head that arises from 

 the lateral surface of the clavicle, but external to the correspond- 

 ing edge of that part of the muscle that arises from the mesial sur- 

 face of the bone. It runs upward and forward, and is inserted 

 along the anterior two thirds of the ventral edge of the ventral 

 wing of the fifth ceratobranchial, its anterior half here lying inter- 

 nal to the pharyngo-hyoideus. Across the outer surface of the 

 muscle, at about one-third its length from its origin, there is 

 usually a broad, irregular, tendinous line, not shown in the draw- 

 ing. 



The pharyngo-clavicularis internus (Pci) arises near the ante- 

 rior edge of the mesial surface of the clavicle, at about the middle 

 of its length. In some specimens there is, on this part of the 

 clavicle, a cornice-like edge projecting backward, which, when 

 found, gives origin to the muscle. The muscle runs upward and 

 forward and is inserted along the posterior half of the ventral 

 edge of the ventral wing of the fifth ceratobranchial, the anterior 

 half or two thirds of the muscle here lying internal to the pharyn- 

 go-clavicularis externus. The fifth ceratobranchial, as shown in 

 Fig. 49, lies considerably below its natural position. 



The two pharyngo-claviculares are innervated by branches of 

 the ramus anterior of the fifth arch, that is, by the ramus post- 

 trematicus of the fourth vagus, the same nerve that innervates 

 the transversus ventralis posterior, and possibly, though it seemed 

 not probably, the pharyngo-hyoideus. 



No Interbranchiales are described by Vetter in any of the 

 teleosts examined by him. They are apparently represented, in 

 Scomber J by two sets of muscles, one of which is greatly degener- 

 ated, and the other specialized in relation to the gill rays. The 

 former are found on the anterior faces of each of the first four 

 arches, along the bases of those gill filaments that lie at the outer, 

 posterior angle of the arch. The muscle on each arch is repre- 



