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KAMAKICHI KISHINOUYEJ 
The epihyal is a flat, triangular bone united anteriorly by means of long 
and fine tooth-like processes with the ceratohyal, and posteriorly with a joint 
to the stylohyal. This bone carries three branchiostegals. The vascular 
groove near the upper margin is distinct in the Scombridæ and Cybiidæ ; but 
indistinct in the Plecostei. The bone is short and broad in the Plecostei, 
especially in the Katsuwonidæ. 
The interliyal is a small bone, connecting the hyoid arch through an 
intervening cartilage with the hyomandibular and the symplectic. In the 
Scombridæ the bone is styliform, more or less flattened below, in the Cybiidæ 
broad and more or less flattened, in the Thunnidæ flat, nearly triangular with 
a lamellar extension on the posterior side, and in the Katsuwonidæ flattened, 
and more or less rectangular in shape. 
The urohyal is a median, laterally compressed, elongated bone gradually 
wideniDg posteriorly. It is joined to the hypohyals at the anterior end, but 
free at the posterior end, furnishing a surface for the attachment of the muscle 
of the isthmus or the throat. 
The branchiostegals are flat, slender, curved bones, spanning the 
membraneous fringe at the mouth of the gill-slit. They are seven in number, 
and are longer, broader, and more curved posteriorly. 
Branchial Arches. 
The branchial arches support the gill-lamellæ, and are situated below 
the cranium, enclosed within the hyoid arch. The general aspect of the 
branchial arches seems to differ only a little in different groups of the 
scombroid fishes ; but if we examine these arches more closely, the difference 
among the different groups becomes very distinct (fig. F). 
The basibranchials (fig. G) consist of three ossicles in a linear series 
along the median line. The first is joined to the ceratohyals of the hyoid 
arch by means of a cartilaginous front end. The second is generally shortest, 
and the third longest. The second has an oblique groove on each side for 
the attachment of the first branchial arch. The third ossicle has also an 
oblique groove for the attachment of the second branchial arch near the 
anterior end. In the Scombridæ the basibranchials are narrow, laterally 
compressed, and more or less straight. The grooves for the attachment of 
