314 
KANAKICHI KISHINOUYE : 
surface of the bone. This character, however, is not found in Grammcitorcynus. 
In the Cybiidæ there is a pair of accessory crests between the temporal and 
pterotic crests, except in Sarda and Gyrnnosarda. And this accessory crest 
is situated rather near the pterotic crest, and is not so conspicuous as in the 
Scombridæ. 
The alisphenoids are paired bones, forming the anterior part of the floor 
of the brain-cavity, situated on both sides of the ventral median foramen. 
Generally they do not meet at the median line, but are separated by a large 
foramen. They are bounded by the frontals at the anterior end, by the 
sphenotics at the exterior side, by the prootic and basisphenoid at the 
posterior end, and by the supraoccipital at the dorsal side in Gyrnnosarda 
and Plecostei. The alisphenoids of the scombroid fishes never come in contact 
with the prefrontals, though Masterman (56) states that the alisphenoids of 
the common European tunny extend from the prootics behind to the 
prefrontals in front. In the Scombridæ the alisphenoids are a little longer 
than broad, nearly flat, and separated from the supraoccipital. In the 
Cydiidæ the inner, anterior end of the alisphenoids is more or less turned 
downward, and in Cybium niphonium (fig. A 2) and C. Icoreanum these bones 
meet in the anterior median line, and are fir ml} 7 joined together over the root 
of the olfactory nerve. In the Thunnidæ (fig. A 3) the inner margin of the 
alisphenoid is produced downward, and meets with that of the opposite side 
in the median line, to form a median ventral wall, separating the ventral 
median foramen into two, the small anterior for the olfactory nerve, and the 
large posterior for the optic. In the Katsuwonidæ the alisphenoids end in a 
thick pointed process produced along the ventral side of the frontals, and the 
posterior part is divided into two horizontal sheets. The ventral sheet ends 
almost free ; but iu Euthynnus it meets .with a special broad process of the 
prootic. In the Cybiidæ and Plecostei the alisphenoid has a dorsal branch 
at the anterior end. This dorsal branch and the anterior ventral branch grasp 
the thickened end of the frontal. In the Scombridæ the alisphenoids do not 
reach the median uniting line of the frontals ; but in the Cybiidæ and 
Plecostei they reach the posterior end of the median uniting line of the 
frontals and are produced a little further anteriorly below the frontals. 
The parasphenoid is a very long bone, running nearly the whole length 
