Key to the Japanese genera 



ao The cutaneous blood vessel passes through the myotome of the 

 fifth vertebrao There are groups of small blood vessels on 

 the su rf ace of the liver oooooo3oo.ooooooooo<>o<.»o»oo»»o»(> a 



bo The subcutaneous blood vessel passes through the myotome of 

 the seventh vertebrao There are no clusters of small blood 

 vessels on the surface of the liver o • o. o <, o 0..0 ...... o ». j » » D' 



a' Pectorals short, roughly equal to the head length, tips 

 not reaching to beneath the anterior edge of the base of 

 the second dorsal c Second dorsal and anal lowo The 

 number of gill-rakers is generally 12 / 35 - 57o . „ .. Thunnus 



b" Pectorals remarkably longs ribbon-like in shape , reaching 

 to the anterior dorsal and anal finletso The second dorsal 

 and anal are of moderate height„ Gill-rakers are 9 / 18 = 

 27 ,.,.........<, o ..... , . Germo 



b' The posterior cardinal vein does not join with the Cuvierian 

 ducto There are clusters of small blood vessels on the 

 inner surface of the livero The pectorals are longj, 

 reaching about to the posterior edge of the second dorsal 

 basec The second dorsal and the anal are of moderate 

 heighto The dorsal and anal finlets are tinged with yellow 

 but not bright o In most cases the gill-rakers are 



b" The posterior cardinal vein and the Cuvierian duct joino 



There are plexuses of small blood vessels in the haemal canal. 

 The gill-rakers are 6 -9 / 17-21 e 23 =• 30 „ . Neothunnus 



Thunnus South 1845 



The body is a long ellipse in outline and is very plumpc The caudal 

 peduncle is remarkably slendero The head is almost conicalj and the 

 mouth is largeo In both jaws there is a single row of small conical 

 teethj and on the vomer and palatines there are minute villiform teeth 

 and areas of sandpaper-like teetho There are scales, and the corselet 

 is indistincto The pectorals are remarkably short„ The gill-rakers in 

 most cases are 12 / 25 - 37o There is only the following single species 

 in Japanese waterso 



Figure 7o-" Thunnus orientaliso 



lo Thunnus orientalis (Schlegel) 



This fish has the names maguro, kuromagurOg omaguro , kuroshibi, , 

 and gotoshibij while the young specimens are called meji ^ yokowa ^ and 

 kakinotaneo 



26 



