COMPARATIVE STUDY OF SCOMBROID FISHES. 
321 
The palatine lies on the external side of the vomer and holds the head 
of the maxillary fast, with the bent and nearly bifurcated anterior end. In 
the Scombridæ the bone is nearly flat in the plane of the mesopterygoid ; but 
in the other scombroid fishes its free ventral margin is generali} 7, armed with 
teeth on a ridge, projecting and more or less vertical to the principal part of 
the palatine, and also to the plane of the mesopterygoid. 
The pterygoid is generally a T-shaped bone, united to the palatine with 
a slender horizontal shaft. The posterior end is expanded and joins to the 
inner side of the metapterygoid and quadrate, with a rough surface. 
The mesopterygoid is a flat thin bone united to the palatine and 
pterygoid, and rests on the parasplienoid with the internal free margin. It is 
very remarkable that the bone is armed with an elliptical patch of villous 
teeth at its centre in the Thunnidæ, as the bone is not armed with teeth in 
other fishes. 
The hyomandibular is a stout bone, with a broad upper portion, and a 
more or less rod-like lower portion. The broader portion has three conspicuous 
condyles, of which the anterior and middle are for the cranium, and the 
posterior one for the opercle. In the Scombridæ the hyomandibular is broad, 
Fig. B. External view of the hyomandibular. 1, Scomber jnponicus', 2, Acanihocylium solan- 
dri ; 3, Cybiurn niphonium ; 4, Sarda orientalis; 5, Xcothunnus macroplerus ; 6, Katsmconus pelamis. 
