ip8 ALUS. [Vol. XVIII. 



extending backward a short distance from the symphysis. It 

 arises, on each side, near the 'dorsal edge of the dentary, in a 

 sHght longitudinal depression in that bone, and lies between the 

 tendons by which the two parts of the geniohyoideus have their 

 insertion. 



The Geniohyoideus presents, as in Ainia, two portions, a 

 superficial, inferior portion and a deeper, superior one; but these 

 two portions of the muscle, in Scomber, and the muscles of op- 

 posite sides of the head, are much more fused with each other 

 than they are in Aniia. 



The superior, or deeper portion of each muscle (Ghs, Figs 56- 

 58) arises by two more or less distinctly marked heads from the 

 outer, ventro-lateral surface of the ceratohyal of its side of the 

 head, slightly in front of the base of the fourth branchiostegal 

 ray. One of these t-\^o heads is entirely muscular, the other en- 

 tirely tendinous. The former is much the larger of the two and 

 arises from the external surface of the ceratohyal in a narrow 

 line which runs transversely from the ventro-posterior edge of 

 the bone forward and upward somewhat more than half way 

 across it. The other, or tendinous head of the muscle arises more 

 from the integument that lines the mouth cavity than from the 

 ceratohyal, the integument, however, being firmly attached to 

 the ceratohyal at the place or origin of the tendon. This place of 

 origin is on the external surface of the ceratohyal, near the dorso- 

 anterior edge of the bone, usually about opposite the middle of 

 the line of insertion of the muscular head. The groove that 

 lodges the arteria hyoidea, and hence that artery also, lies between 

 the two surfaces of origin. Both parts of the muscle run mesially 

 and forward along the external surface of the ceratohyal, and 

 soon unite more or less completely. The ventral, muscular head of 

 the muscle here becomes entirely tendinous, and for a short dis- 

 tance the entire muscle is simply a broad, flat tendon. From this 

 tendon the anterior, wholly muscular part of the muscle arises. 

 The fibers of this anterior part of the muscle are in part inserted, 

 with the fibers of the corresponding muscle of the opposite side of 

 the head, in a median aponeurosis ; but a large part of them con- 

 tinue forward and are inserted, with the corresponding fibers of 

 the opposite muscle, on a relatively small, flat and narrow, median 



