312 
KAMÀKICHI KISHINOUYE: 
In the Cybiidæ the skull is elongated, low, and flat, especially in the 
ventral, temporal region. Generally the length of the skull is contained more 
than 1*- times in its breadth. The dorsal crests are well developed, mostly 
u 
running more than half the length of the frontals, and nearly parallel to each 
other. In the Plecostei the skull is short, only a little longer than broad,, 
much broader than high, and we find high ridges and deep depressions on 
its ventral side or the auditory region of Mastebman. The development of 
these ridges and grooves differ greatly in different species. There are three 
foramina on the dorsal side of the skull, except in the genus Auxis. The 
inner dorsal or temporal crests diverging forward, while the outer ridges are 
converging ; but in the Ivatsuwonidæ the inner ridges are nearly parallel to 
each other. The pterotic processes are long, flat, and flexible, especially in the 
Ivatsuwonidæ. In the Cybiidæ and Plecostei the posterior ends of the temporal 
and pterotic crests are connected with a straight ridge on each side of the 
skull, and the space between these two crests is nearly flat. In the Cybiidæ 
and Plecostei the dorsal surface of the skull is almost entirely covered with 
the lateral muscle, except in the cases of Grammatorcynus, Acanthocybium, and 
Gymnosarda. In the Plecostei there is a special chamber, posterior to the 
myodome, and below the basioccipital. The sides of the chamber are formed 
by the parasphenoid. So I shall name this chamber the parasphenoidal 
chamber. On the ventral side of the cranium, there are very deep depressions 
in the otic region. These depressions are quite peculiar to the Plecostei. 
The ethmoid is a median bone, bounded by the frontals above, by the 
prefrontals at the lateral and posterior sides, and by the vomer and para¬ 
sphenoid below. It has paired horn-like processes with a condylar surface for 
the maxillary at their, ventral surface. In the Scombridæ, however, the condylar 
surface for the maxillary is found it the lateral ventral margin. The dorsal 
exposed surface of the ethmoid is crescent-shaped or Y-shaped in the Cybiidæ ; 
but it is more or less trapezoidal in the Plecostei. Tho concavity at the front 
edge of the exposed dorsal surface of the ethmoid is to receive the premaxillary 
processes. 
The prefrontals are paired bones, forming the anterior wall of the orbit, 
and lie between the vomer, parasphenoid, ethmoid, and the anterior part of 
the frontals. Generally they are massive, but in Scomber' and Gymnosarda 
