342 KAMAKICHI KISHrSOUYE: 



second veiiebra, instead of the third. In tliis family the tips of long anterior 

 intermuscular bones overlap each other at the external sm-face of the lateral musele. 

 In Cylitmi the intermusclar bones are scarcely developed in the caudal region 

 (fig. 6), and the anterior intermuscuW bones are turned more or less up-ward. 

 In other scombroid fishes the intermuscular Ixjues almost he in one plane. In 

 Sarda intermuscular bones are very •well developed. They are thick and long 

 in the anterior precaudal region. In Acardhocybitim solandn the intermuscular 

 bones are ten in number, and axe fovmd in the precsiudal r<^on only ; but in 

 Sarda and Gymnosarda they axe found in the caudal paii too. 



In the Plecostei the ribs are broad, doreoventrally compressed, and 

 gradually attenuated towaxds the posterior, internal side. They he close to 

 each other and do not hang down along the jjei'itoneiun, but they thatch the 

 roof of the abdominal cavity. In the Thuunidae the proximal portion of 

 one or two ribs, lying just before and above the root of the cutaneous 

 axtery, is very slender, so as not to obstruct tlie free passage of the blood. In a 

 lai"ge specimen of Tlninnus orientalis I found that the fifth and sixth ribs con- 

 sist of two paiis. The short, slender, proximal paxt lies at the anterior slo^ie 

 of the hypaxial portion of the lateral muscle, which is rather suddenly developed 

 from the myotome of the seventh vertebra. Those are probably abnormal. 

 The intermuscular bones are develop-d from the cephalic region to the candt^I 

 region, and they are imited to the lateral median line of the veiiebral cohuun, 

 and each pair at the anterior margin of the centnun of each vei*tebra, except 

 in the first vertebra, in which these bones ai'e attached to the ueinral arch. 

 These bones are long, slender, and their distal ends lie at the external sirrface 

 of the lateral muscle in the anterior pai"t of the body (figs. 2-5) ; Imt the 

 majority of them have their distal end at the boimdary between the su)^)erficial 

 dai'k red muscle and the profoimd dark red muscle. The intermuscuLvr bones 

 foimd anterior to the seventh vciiebra are long, and appear on the SOTface of 

 the lateral muscle, while those posteiior to the seventh vertebra become short 

 rather suddenly, and ia the case of Katsnwouidae the List two to seven of 

 those intermuscular lx)ncs are dividal into two portions (%. 5) ; the pmi 

 beyond the profound dark muscle is separate from the proximal part jiud these 

 two paais are connected with a hgament. Intermuscular bones on tlie third 

 and fom^h vertebrae are fused to the dorsal side of the head of tlic resp native 



