152 ALUS. [Vol. XVIII. 



abuts against and is closely and firmly bound to the anterior sur- 

 face of the rod-like body of the hyomandibular, but its inner sur- 

 face does not touch the outer surface of the thin, anterior part 

 of the latter bone, a narrow space being left, into which fibers of 

 the levator arcus palatini pass. This space between the two bones 

 is also traversed by the dorsal end of the arteria hyoidea. From 

 the inner surface of this part of the bone, a little below its dorsal 

 end, a strong process arises. It projects almost directly backward, 

 lies closely against the inner surface of the rod-like part of the 

 hyomandibular, and, behind that bone, slightly overlaps the an- 

 terior edge of the inner surface of the preoperculum. This process 

 and the dorsal portion of the metapterygoid, lying respectively 

 against the inner and the outer surface of the hyomandibular, hold 

 that bone firmly and immovably between them. The hind edge of 

 the metapterygoid is thus here, in a manner, grooved, and as the 

 groove lodges an artery, the arteria hyoidea, it may be that this 

 part of the metapterygoid corresponds to the grooved dorsal sur- 

 face of the proximal elements of the other arches, as already stated. 



The dorsal end of the metapterygoid seems, from its relation 

 to the levator arcus palatini, and the fact of its being capped with 

 cartilage, to correspond to the so-called dorsal process, or meta- 

 pterygoid process, of the metapterygoid of Ainia. 



The inferior end of the hind edge of the metapterygoid abuts 

 against the inferior end of the hyomandibular, and against the in- 

 terspace of cartilage between that end and the dorsal end of the 

 symplectic. Between this postero-inferior corner of the meta- 

 pterygoid and the posterior process near its dorsal end, the hind 

 edge of the bone does not touch the hyomandibular, a relatively 

 large slit being left between the two bones. Through this slit, 

 as already stated, the dorsal end of the arteria hyoidea passes in- 

 ward and upward from the outer to the inner surface of the 

 palato-quadrate arch. 



The inferior edge of the metapterygoid has three regions or 

 portions. One is directed backward and downward, one down- 

 ward and somewhat forward, and one forward and somewhat 

 downward. The middle one of the three portions is slightly con- 

 cave, is concentric with the superior edge of the quadrate, and, 

 in large fishes, is separated from that edge by only a narrow line 



