COMT-VRATIVE STUDY OF SCOMBROID FISHES. 327 



bebiud the glossoliyal, and is composed of two pieces, upper aud lower. Tlio 

 former is nanx)w, while the latter ia broad. In the Scombridje the lower 

 piece has a pair of processes at the posterior margin, growing just in opposi- 

 tion, to grasp the anterior end of tlie ceratohyal. The inner process is broader 

 than the outer. In the Cybiidae the lower piece rest partly on the anterior 

 lower process of the ceratohyal. In the genus Cybium the postei'ior upp^r 

 comer of the up]Ter piece is produced to a pointed process. In the ThunnidiO 

 the upper piece is largely covered by the lower piece from the exterior side. 

 The posterior margin is nearly straight. In the Katsuwonidce the lower piece 

 Las a posterior process which fits tightly to a hoiizontil slit at the anterior 

 part of the ceratohyal. 



The ceratohyal is a long flat bone, broader at the posterior end. Four 

 anterior branchiostegals are attached to this bone. In the Scombridre ;xnd 

 Cybium, the dorsal siu'face of the ceratohyal is nearly sti-aight, while in the 

 other scombroid fishes it is concave. 



In the ScombridcB the anterior margin of the ceratohyal is nearly straight ; 

 but in the other scombroid fishes this lx>ne lias a long process fi'om the 

 anterior lower margin. The ceratohyal is united with the epihyal by means 

 of many fine teeth fi'om both bones, and also the cartilage lying between 

 them. Tlie teeth are larger and more numerous on the inner side. On the 

 external side and near the upper margin there is a narrow groove to receive 

 blood-vessels. In the Cybiidie the ceratohyal unites with the epLhyal by 

 means of long teeth on both the inner and outer sides, except in Sir da and 

 Gymnosarda. In the latter genera the outer teeth are not found. The groove 

 for bluod-vessels is distinct, and sometimes a part of the gi'oove is pierced, as 

 in Cybium niphoimim and Gymnosarda nuda. In the Thunnidse the tooth-like 

 processes for the aiiiculation with the epihyal are found on the inner side only, 

 as in So.rda and Gymnosarda. At the venti'al margin we find two or 

 thi'ee projeetioijS, which are inconspicuous in the Cybiidfe. The vascular groove 

 is indistinct, but in TInmmts and Paratlmnnus a slit is found in the place. 

 In XcotJcunnus a gi'oove or a slit is hardly visible. In the Katsuwonidte 

 tooth-like processes for articulation are found on both sides. No sUt nor 

 groove is found. Tooth-like processes at the venti'al margin are rather 

 conspicuous. 



