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KAMAKICHI KLSHINOUYE : 
bone is the largest opercular bone, broadest at the middle, and tapering 
gradually and nearly equally towards both extremities. In the Cybiidæ 
the horizontal limb is wide near the dorsal end. In the genus Cybium the 
preopercle is very broad at the lower posterior angle. In the Thunnidæ the 
horizontal limb is well developed ; but smaller than the vertical. In the 
Katsuwonidæ the horizontal limb is better developed than the vertical, and 
both limbs taper nearly equally towards the extremities. The posterior and 
ventral margins of the opercular bones are attenuated and roll inward when 
dried. 
Hyoid Arch. 
The glossohyal is a small median bone, embedded in the substance of 
the tongue, with a narrow cartilage at the broad anterior end. In the 
Scombridæ the bone is especially Small, and more or less spatulate. In 
the Cybiidæ the bone is generally rod-like, thick at the proximal part ; but in 
Sarda orientalis it is spatulate. In Gymnosarda nuda the glossohyal is nearly 
covered from both sides with the inner edge of paired semicircular dentigerous 
ossicles. The front margin of the glossohyal is nearly straight in the 
Plecostei. In the Thunnidæ the glossohyal is spatulate, slightly concave above 
and below, and constricted at the posterior end. In the Katsuwonidæ the 
bone is also spatulate, slightly concave in the cross-section. 
The hypohyal forms the symphysis with its fellow of the other side 
Fig. E. External view of the hyoid arch. 1, liastrelliger chrysozonus ; 2, Scomber 
japonicus ; 3, Acanthocybium solandri ; 4, Oybium niphonium ; 5, Sarda orientalis ; 6, Gymnosarda 
jT_ nuda ; 7, Neothunnus macropterus ; 8, Katsuwonus pelamis. 
