328 KAMAKICHI KLSHKOUYE:: 



The epUiyal is a flat, fciiaugiüar bone united anteriorly by means of long 

 and fine tootb-like processes with the ceratohyal, and posteriorly with a joint 

 to the stylohyal. This Iwne carries three branchiostegals. The vasc-ular 

 groove near the upper margin is distinct in the Scombrida3 and Cybiidfe ; Init 

 indistinct in the Plecostei. The bone is short and broad in the Plecostei, 

 especially in the Katsuwonidse. 



The interhyal is a small bone, connecting the hyoid arch through an 

 intervening cartilage Avith the hyomandibular and the symplectic. In tlie 

 Scombridse the bone is styliform, more or less flattened below, in the Cybiid» 

 broad and more or less flattened, in the Thunnidse flat, nearly ti-iangular with 

 a lamellar extension on the posterior side, and in the Katsuwonid;e flattened, 

 and more or less rec-tangular in shape. 



The ra-ohyal is a median, laterally compressed, elongated bone gi'adually 

 widening posteriori}'. It is joined to the hypohj'als at the anterior end, but 

 free at the posterior end, fui-nishing a sm'face for the attachment of the muscle 

 of the isthmus or the throat. 



The branchiostegals are flat, slender, cm-ved bones, spanning the 

 membraneous fringe at the mouth of the gill-slit. They are seven in nimiber, 

 and are longer, broader, and more curved posteriorly. 



Branchial Arches. 



The branchial arches suj^port the gill-lamellffi, and are situated below 

 the cranium, enclosed within the hyoid arch. The general aspect of the 

 branchial arches seems to differ only a Uttle in different groups of the 

 scombroid fishes; but if we examine these arches more closely, the diflerence 

 among the different groups becomes very distinct (fig. F). 



The basibranchials (fig. G) consist of three ossicles in a linear series 

 along the median line. The firet is joined to the ceratohyals of the hyoid 

 arch by means of a cartilaginous front end. The second is generally shoi^test, 

 and the third longest. The second has an obhque groove on each side for 

 the attachment of the fii-st branchial arch. The third ossicle has also an 

 oblique groove for the attachment of the second branchial arch near the 

 anterior end. In the Scomltrid» the basibranchials are narrow, laterally 

 compressed, and more or less sti-aight. The grooves for the attachment of 



