Nos. IAND2.] ANATOMY OF SCOMBER SCOMBER. 153 



of cartilage. This line of cartilage is continued backward and 

 upward along the posterior portion of the inferior edge of the 

 metapterygoid, and, at its dorsal end, is continuous with the inter- 

 space of cartilage that lies between the hyomandibular and sym- 

 plectic. Ventral to that interspace the line of cartilage fits into a 

 groove on the antero-dorsal edge of the symplectic, the cartilage 

 and bone here being simply contiguous, and not continuous one 

 with the other. Anteriorly the line of cartilage that bounds the 

 metapterygoid becomes enlarged into a somewhat trapezoidal in- 

 terspace, which lies between the metapterygoid dorso-posteriorly, 

 the quadrate ventro-posteriorly, the ectopterygoid ventro-anteriorly 

 and the entopterygoid dorso-anteriorly. 



The concave dorso-anterior edge of the metapterygoid is some- 

 what thickened, and has a more or less pronounced groove running 

 obliquely across it from the outer surface of the bone backward 

 to its inner surface. The groove forms the surface of insertion of 

 the adductor arcus palatini. The outer surface of the bone, imme- 

 diately postero-ventral to its dorso-anterior edge, is somewhat 

 concave. 



The Quadrate (Q) is, in shape, the sector of a circle the center 

 of which lies at the inferior end of the bone. This latter end of the 

 bone is enlarged, and presents, antero-ventrally, an articular sur- 

 face which is convex in a longitudinal direction and concave trans- 

 versely. It is lined with cartilage and articulates with a corre- 

 sponding surface on the dorsal surface of the hind edge of the 

 articular. Starting from this articular head, and running upward 

 and backward near the ventro-posterior edge of the quadrate, 

 there is a thickened portion, grooved on its inner surface, and 

 often, but not always, strongly raised and convex on its outer sur- 

 face. The dorsal end of this thickened portion, posterior to the 

 groove on its inner surface, is continued dorso-posteriorly, be- 

 yond the body of the bone, as a strong process, the base of which 

 may adjoin, in part, the cartilaginous line that separates the quad- 

 rate and metapterygoid. The dorsal end of this process is 

 pointed, lies in the depression on the inner surface of the anterior 

 edge of the preoperculum, and is covered or capped with what 

 seemed, in certain specimens, to be simply fibrous tissue, but in 

 others to be cartilage. 



