The metapterygoid is broadj its dorsal edge is bif\trcate and 

 embraces the rod-shaped portion of the hyomandibular. The quadrate 

 is flat and roughly triangular in forme, At its anterior corner 

 it has a marked saddle=shaped portion for articulation with the 

 lower jawo Its lower side has a shallow groove to receive the 

 anteroventral portion of the preopercleo The symplectic is a 

 small bonea Its anterior portion is sword-shaped and fits into 

 the lower part of the quadrate^, but the posterior portion is more 

 or less flat., The lower edge is thick and is connected by carti- 

 lage to the lower end of the hyomandibularc 



The articular is a stout bone wtiichg together with the dentary, 

 forms the lower jaw„ It has three processes projecting anteriorlyo 

 The upper and lower processes are small with gradually tapering 

 tipso The middle process is large and its tip is embraced by the 

 dentarj'o Posteriorly it has a large concave articulating surface 

 which articulates with the quadrateo The small angular bone is 

 firmly attached to the posterior inferior portion of this bone,, 



The dentaries form the tip of the lower jaWj, the right and 

 left bones articulating at the tipo The posterior part is large 

 and bifurcate, embracing the middle process of the articular, On 

 the dorsal surface of this bone,, that is the portion which is 

 opposed to the upper jaw^ there is a single row of sharp teeth 

 which are curved inwardo 



Of the various bones which make up the gill covers the opercla 

 is a flat bone roughly square in shapeo Its anterior angle has 

 an articulating cavity for the hyomandibular^ The subopercle 

 presents a rather triangular foniio Its upper edge is covered by 

 the operclej, its anterior edge by the interoperolej, and its 

 posterior edge is free.. The interopercle is oval in shapes its 

 lower edge is slightly serrate and forms the lower edge of the gill 

 covero This bone is joined to the posterior end of the hyoid aroh by 

 a ligamento In the tuna (black tuna) its posterior edge is convex 

 but in the other species it is fairly straights The preopercle 

 is a large curved bonej the vertical edge of which fits into a 

 groove in the hyomandibular while its horizontal edge is Joined 

 to the pterygoid and quadrate^ 



Of the various bones that make up the hyoid arch^ the glosso= 

 hyal is a single small bone which is buried in the tongueo It is 

 roughly spatulate in shape and its upper and lower edges are almost 

 straight-o The hypohyal is posterior to the glossohyal and the 

 right and left bones are fused togethero This bone is made up of 

 two pieceS; an upper and a lowero The upper is narrow end the 

 lower is broadp covering a good deal of the upper one.. The cera= 

 tohyal is one long flat bone with a broad posterior tipo Its upper 

 edge is concave and there is a long process on the lower anterior 

 edge. This bone and the epihyal are joined by fine serrate inden- 

 tations and projectionso The four most anterior of the branchios- 

 tegal rays are supported on this bone;. The epihyal is a flat 



