The first dorsal fin is well developed with delicate raysc Just 

 posterior to the anterior end of the fin, which is its highest portion, 

 the length of the fin rays decreases rather suddenly^ but thereafter j, 

 in the central portion of the fin, the height of the fin rays increases 

 graduallyo At the posterior end of the fin, the height of the rays 

 again decreases graduallyo Consequently^, the profile of the first 

 dorsal fin is concave in its anterior portion and arcuate in its pos= 

 terior portiono The pectoral fins are remarkably shorty their length 

 being about Oo 8 times the body depths The ventral fins are conspicuously 

 longer than the pectoral finso The first anal fin is well developedo 

 The falciform second dorsal and anal fins are located diametrically 

 opposite each other and are of approximately the same shape and sizoo 

 The caudal fin is large and strongj its upper and lower lobes being 

 narrow in width but broadly forkedo 



There are rasp-like teeth on both the upper and lower jaws and 

 a patch of slender brush=like teeth on the palatinoo The cranium is 

 somewhat longer and narrower than in other specieso The vertebrae are 

 long and both the haemal and neural s pines are roughly rhomboid in 

 shapeo The gonads are Y-shaped, with the left side longer than the 

 righto The right gonad joins the left above the vento 



The dorsal surface is steel blue and the belly is silvery-whiteo 

 The boundary between these two colored areas is a rather distinct^ 

 finely serrated line which runs straight along the side of the body 

 somewhat above its median linoo 



This species occurs from Sagami Wan southo It is extremely 

 pelagic by nature j and hardly ever enters coastal sea areas or 

 enclosed waters,. It is rather abundant from October through December 

 in the waters east of Formosa^ at which time and place it spawnso 



This species attains a length of lp500 millimeters and a weight 

 of 20 kilograms. 



This fish has been reported as a new species by Professor Tanaka, 

 howeverj morphologically it is extremely close to To belone of the 

 Atlantic and To brevirostris of the Indian Oceanc It is thought that 

 these probably are all the same species^ but at present it is impossible 

 to confirm thiso 



Genus Istiophorus LacepedOs 1802 



Body long and slender ^ markedly compressed laterally j; the height 

 of the first dorsal fin much greater than the body depths The ventral 

 fins are long and their rays are incompletely fused togethero 



Figure 19»— Sailfish 



57 



