COMPARATIVE STUDY OF SCOMBROID FISHES. 
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behind the glossohyal, and is composed of two pieces, upper and lower. The 
former is narrow, while the latter is broad. In the Scombridæ the lower 
piece has a pair of processes at the posterior margin, growing just in opposi¬ 
tion, to grasp the anterior end of the ceratohyal. The inner process is broader 
than the outer. In the Cybiidæ the lower piece rest partly on the antorior 
lower process of the ceratohyal. In the genus Cybium the posterior upper 
comer of the upper piece is produced to a pointed process. In the Tliunnidæ 
the upper piece is largely covered by the lower piece from the exterior side. 
The posterior margin is nearly straight. In the Katsuwonidæ the lower piece 
has a posterior process which fits tightly to a horizontal slit at the anterior 
part of the ceratohyal. 
The ceratohyal is a long flat bone, broader at the posterior end. Four 
anterior branchiostegals are attached to this bone. In the Scombridse and 
Cybium, the dorsal surface of the ceratohyal is nearly straight, while in the 
other scombroid fishes it is concave. 
In the Scombridæ the anterior margin of the ceratohyal is nearly straight ; 
but in the other scombroid fishes this bone has a long process from the 
anterior lower margin. The ceratohyal is united with the epihyal by means 
of many fine teeth from both bones, and also the cartilage lying between 
them. The teeth are larger and more numerous on the inner side. On the 
external side and near the upper margin there is a narrow groove to receive 
blood-vessels. In the Cybiidæ the ceratohyal unites with the epihyal by 
means of long teeth on both the inner and outer sides, except in Sir da and 
Gymnosarda. In the latter genera the outer teeth are not found. The groove 
for blood-vessels is distinct, and sometimes a part of the groove is pierced, as 
in Cybium niphonium and Gymnosarda nuda. In the Thunnidæ the tooth-like 
processes for the articulation with the epihyal are found on the inner side only, 
as in Sarda and Gymnosarda. At the ventral margin we find two or 
three projections, which are inconspicuous in the Cybiidæ. The vascular groove 
is indistinct, but in Thunnus and Parathunnus a slit is found in the place. 
In Neothunnus a groove or a slit is hardly visible. In the Katsuwonidæ 
tooth-like processes for articulation are found on both sides. No slit nor 
groove is found. Tooth-like processes at the ventral margin are rather 
conspicuous. 
