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KaMAKICHI KISHINOUYE : 
at the dorsal margin to fit to a lateral ventral process of the prefrontal. The 
dorsal margin of these bones is rather thick, but the ventral margin is very 
thin. These bones protect the lower side of the eyes. 
The suborbital ring of bones is more or Jess conspicuous in the Scombridæ, 
but in the other groups of the so-called scombroid fishes the ring is inconspicuous, 
as the bones of the ring are not much differentiated from scales on the cheek. 
* 
Jaw Bones. 
In the Scombroid fishes the premaxillary is a long, curved bone, with a 
long thick head. The bone becomes gradually narrow behind, and without 
any marked prominence or groove. In the Scombridæ the bone is very thin, 
slender, and its head is low and blunt. In the Cybiidæ it is massive, and 
its head is also low. In that family in general the anterior end of the 
premaxillary is sharply pointed and the dorsal tip of its head is oblique and 
pointed. In the Plecostei the anterior head of the premaxillary is large, 
blunt, and thick, while the remaining part is laterally compressed, and 
comparatively narrow. 
The maxillary is also a long, curved bone with a thick hollow head, lying 
on the premaxillary. The shaft of the bone is thin and narrow at the 
posterior end, but thick and grooved at the anterior part. In the Scombridæ 
the maxillary differs greatly from that of the other scombroid fishes. The 
head is small, its excavation shallow, while the shaft is uniformly flat and 
broad, and has an indentation at the posterior ventral margin. The dorsal as 
well as the ventral margins of the bone are trenchant. In the other scombroid 
fishes the dorsal margin of the maxillary is generally rounded. In the Cybiidæ 
the head of the maxillary is generally low, grooved at the ventral side for the 
greater part, and the posterior end of the shaft is broad and flattened. In 
the Plecostei the maxillary has the head thicker and larger, and the dorsal 
margin of the shaft is trenchant in the middle, the ventral margin move or 
less grooved. The auxiliary bone to the maxillary, called jugal by Master- 
wan, is very small, narrow, and insignificant in the Scombridæ ; but in the 
other families of the scombroid fishes it is comparatively large and broad. It 
is pointed at the anterior end and attached to the dorsal posterior corner of 
the maxillary. 
