Nos. IAND2.J ANATOMY OF SCOMBER SCOMBER. 201 



of the head Hes superficial to, that is ventral to, that of the right 

 side, as in Ainia. The other, deeper part of the inferior muscle 

 arises from the ventral surface of the most anterior or next ioU 

 lowing ray, runs forward, or forward and laterally and is in- 

 serted partly on the ventro-posterior edge of the distal end of the 

 ceratohyal, and parth^ on the adjoining and corresponding edge 

 of the proximal end of the hypohyal. In Fig. 58 a part of this 

 muscle, on the right hand side of the fish, is seen arising by a 

 separate tendon. This is exceptional. The fibers of this deeper 

 part of the muscle lie at a considerable angle to those of the 

 superficial portion, and the two parts of the muscle, together, 

 are apparently equivalent to the single muscle of Amia. 



The superior division of the hyohyoideus is a thin layer 

 of somewhat separate muscle bundles, extending from ray to ray 

 along the inner surface of the gill cover. It is most developed 

 near the bases of the branchiostegal rays, and extends distally on 

 them for only about one third or one half their length. In part 

 it arises, as in Amia, from the adjoining, ventro-posterior edge 

 of the ceratohyal. Toward the free ends of the branchiostegal 

 rays it disappears entirely, and near the proximal end of the 

 ceratohyal it becomes a sheet of degenerate muscle tissue, or 

 simply a series of patches of such tissue. From the dorsal edge 

 of the last, or most dorsal branchiostegal ray, a sheet of this 

 degenerate tissue extends upward to the inner surfaces of the 

 interoperculum and suboperculum. Two other detached patches 

 of similar tissue are found on the inner surface of the operculum, 

 one lying posterior to the surface of insertion of the levator 

 operculi, and the other at the hind edge of the operculum and ex- 

 tending across the notch in the hind edge of that bone. 



The Adductor Hyomandibularis {Ah, Figs. 11 and 55) and 

 Adductor Arcus Palatini (Aap) are, in Scomber, simply re- 

 gions of a single continuous muscle. Nothing whatever, at the 

 origin of the muscle, indicates a separation of its two parts, and 

 such a separation, at its insertion, is indicated only by the fact 

 that the posterior part of the continuous muscle is inserted on 

 the inner surface of the hyomandibular, while the anterior part 

 is inserted on the inner surface of the palatine arch. That part 

 of the muscle that has its insertion on the inner surface of the 



