312 KAilAKICHI KISHKOrYE: 



In tlie Cybiidso the skull is elongated, low, antl flat, es^xjcially in tho 

 ventral, temporal region. Generally the length of the skull is contained more 

 tlian 1„- times in its breadth. The dorsal crests are well devcloj^ed, mostly 

 running more than half the length of the ft-ontals, and nearly parallel to each 

 other. In the Plecostei the skull is short, only a little longer than broad, 

 much broader than high, and wo find high ridges and dee]: depressions on 

 its ventral side or the auditory region of M.^stermak. 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 Av.xis. The 

 inner dorsal or temporal crests diverging forward, wliile the outer lidges are 

 converging ; but in the Katsuwonidse the inner ridges arc nearly parallel to 

 each other. Tho pterotic processes are long, flat, and flexible, especially in the 

 Katsuwonidw. In the Cybiidse 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 Cybiidse 

 and Plecostei the dorsjil sm-face of the skull is almost entirely covered with 

 the lateral muscle, except in the cases of Grammaiorcynus, Acanikoci/bium, and 

 Gymnosarda. In the Plecostei there is a special chamber, ix)sterior 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 venti-al 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, Ixjimded by the frontals above, by the 

 prefi'ontals at the lateral and j^xjsterior sides, and hy tlie vonier and pai'a- 

 sphenoid l)elow. It has imircd horn-Uke processes with a condylar surfaco for 

 the maxillary at their. ventral siu'face. In the Scombridas, however, the condylar 

 surface for the maxilLiry is foimd it the lateral venti'al margin. The doreal 

 exposed surface of the ethmoid is crescent-shaped or Y-shaped in the Cybiidte ; 

 but it is more or less trapezoidal in the Plecostei. Tlie coucavit}' at the front 

 edge of the exposed dorsal siu'face of the ethmoid is to receive the premaxillar}- 

 processes. 



The prefi'ontals are paired liones, forming the anterior wall of the orbit, 

 and lie between the vomer, parasphenoid, ethmoid, and the anterior part of 

 the frontala. Generally they are massive, but in Scomber and Gymnosarda 



