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COMPARATIVE STUDY OF SCOMBROID FISHES. 
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metapterygoid and quadrate are firmly connected by the intervention of the 
pterygoid and symplectic, with which they unite with zigzag sutures at the 
inner side. 
The quadrate is a flat triangular bone, with a stout, movable, saddle- 
shaped joint at the anterior angle to articulate with the lower jaw. At the 
lower side there is a shallow groove to receive the lower, anterior portion 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 
posterior part, but thickened at the louver margin, and connected with the 
lower end of hyomandibular by a cartilage. 
The articular is a stout bone with a long pointed middle process which 
is partly sheathed in the dentary, two diverging processes at the dorsal and 
ventral sides, and a large concave articulating surface for the quadrate, above 
the knob 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 teeth at the trenchant edge. In the Scombridæ the 
two branches diverge behind, 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 Cybiidæ the bone is comparatively narrow, not 
diverging, and the lower branch is rather shorter and narrower than tho 
upper, except in Sarcla and Gymnosarda. In these genera and also in the 
Plecostei the bone diverges ; but the lower branch is narrower than the 
upper, and the two branches are nearly equal in length. 
Opercular Bones. 
The opercle is a flat bone, more or less trapezoidal in form, articulating 
to the hyomandibular, and is situated behind the preopercle, and above the 
subopercle. The opercle is rather larger, as the gill-opening is very wide. The 
anterior angle of the bone is formed by the articular cup for the hyomandi¬ 
bular, and the posterior angle is the dorsal cod of the line of union with tho 
subopercle. Generally the dorsal and ventral anterior margins and the diagonal. 
