roMPAR.vrivi: s-rrm" of sroMimoiD risiiEs. 323 



mot!i|5terj'goid and qwadnite are firmly connected by the intervention of the 

 pterygoid and symploctic, wnth which they unite with zigzag sutures at the 

 inner side. 



Tlie quadrat« is a flat ti-iaugulai- bone, with a stout, movable, saddle- 

 shaped j lint at the autei-ior angle tj articulate with the lower jaw. At the 

 lower side thoi-o is a sliallow groove to receive tin lower, anterior poi-tion of 

 the preopercle. 



The symplectic is a small bone, styliform at the anterior portion which 

 is wedged into the lower part of the quadrate, more or less flattened at the 

 pDsterior part, but tliickoned a*; tlie loAver margin, and connected with tiie 

 lower end of hyomandibular by a cartilage. 



The articular is a stout lx)uo with a long pointed middle process wliich 

 is partly sheathed in the dentary, two diverging processes at the dorsal and 

 vcntrid sides, and a largo concave articulating siu^Eice for the cpiadrate, above 

 the Icnob at the hind end. 



The angular is a very small bone, firmly joined to the lower posterior 

 corner of the articular. 



The dentary is laterally compressed, forked behind, and always carries 

 only a single row of teoth at the trenchant edge. In the ScombridiB the 

 two branches diverge beMnd, the lower branch being equal to or a little 

 longer than the upper branch. Moreover the lower branch is broader than 

 the upper in Scomber. In the Cybiidae the bone is comparatively nan'ow, not 

 diverging, and the lower branch is rather shoiier and narrower than the 

 upper, except in Sarda and Gymnosarda. In these genera and also in the 

 Plecostei the bone divei'ges ; but the lower branch is narrower than the 

 upper, and the two branches are nearly erpial in length. 



Opercular Bones. 



The opt;rcle is a flat bone, more or less traxx^zoidal in form, articulating 

 t(j the hyomandibular, and is situated behind the preopercle, .and above the 

 subo^xTcle. The opercle is rather larger, as the gill-opening is very wide. The 

 anterior angle of the bone is fjnned by the articular cup for the hyomandi- 

 bular, and the posterior angle is the dorsal end of the lino of union with the 

 suhopercle. Generally the dorsal and ventral anterior margins and the diagonal, 



