OOirPAEATTVE STUDY OF SCOMBROID FLSHES. 453 



fonvjuxl, iusteaJ of turuiny more or less backward as in tlio other plecostean 

 fishes. Each ai'tery reaching to the myotome of the fii^st rib is divided into 

 two arteries, opasial aud hypaxial. The epaxial artery runs below the first 

 rib, while the hypaxial artery runs above the rib. These two arteries, are 

 nearly equally developed, aud arj separated from each other at a distance 

 of 6-8 times the breadth of the blood-vessels. These arteries do not form a 

 loop at the caudal region. The cutaneous artery and cutaneous vein lie 

 in juxtaixjsition, nearly flat at the surfiice of the body. Arterioles and venules 

 ct)nuccted with these cutaneous canids run in opposite dii-ectious, along the 

 surface of the body, and they are not so numerous Jis in the tunnies. The 

 rod of tlie fascular plexus in the haemal canal is called kurochiai by fishermen, 

 and it is thicker than the diameter of the vertebral column. 



This genus is closely allied to the genus Neothunniis of the Thimnidae 

 and stands quite near the genus Euthynnus. Number of the precaudal vertebrae 

 coiTespouds to that uf Eufhynrms, while the number of caudal vertebrae is 

 equal to tlmt of the Thunnidae. Thus the total number of vertebrae is 41, 

 while in all the other genera of the plecostean fishes the number is always 39. 



Only one cosmop<;>Utan species is known from the temperate and tropical 

 regions of the world. 



Katsuwouus pelamis (linnaeus). 



Katsuwo, magatsuwo, mandaragatsuwo. 

 Figs. 5, 14, 19, 25, 52, 57. 



SconJtKr pelamis. Linnaeus. Syst. Nat. X, 297, 175S. 



Thynnus pelamys. Cut. & Val., Hist. Nat. Poiss. VIII, 113, Tab. 214, 1S31 ; Scblegel, Fauna 



Japon. Poiss, 96, Tab. 49, 1850; Günther, Cat. Brit. Mus. U, 334, 18G0. 

 Gymnosardn pelnmit. Dressier & Fesler, Bull. U. S. Fish Comm. VII, 436, 18S9, .Jordan 



& Evermnnn. Fish. X. & SI. .\merica, I, SüS. 1896. 

 Euthyruius pelam'is, Tanaka, Fish. .Japan, I— X, 140, Pis. 37. 39, 40, 1912. 

 Kalsurconus pelamys, Kishinouye, Sui. Gak. Ho, I, 21, PI. 1, Fig. IJ, 1915. 



D. 12-17, 11-14, 8. A. 11-15, 7. Gül-rakers 15-20+36-39. 



Body plump, sharply pomted at both ends. Lateral line slightly curved 

 upward atovo the pectorals and lient below the second dorsal, and nearly 

 horizontixl in the caudal portion. Gill-rakers numerous, very thin, aud their 

 inner margin imdulating. The right lobe of the liver is small and slender. 



Plexus of venules from the posterior cardinal vein forms a long continuous 



