Isthmus Barriers Separating Fish Faunas 257 



the other. The second or Hokkaido* district includes this 

 northern island and that part of the shore of the main island 

 of Hondof which lies to the north of Matsushima and Noto. 

 Here the cold northern currents favor the development of a 

 northern fauna. The herring and the salmon occupy here the 

 same economic relation as in Norway, Scotland, Newfoundland, 

 and British Columbia. Sculpins, blennies, rockfish, and floun- 

 ders abound off the rocky shores and are seen in all the markets. 



South of Matsushima Bay and through the Island Sea as far 

 as Kobe, the Nippon fauna is distinctly one of the temperate 

 zone. Most of the types characteristically Japanese belong here, 

 abounding in the sandy bays and about the rocky islands. 



About the islands of Kiusiu and Shikoku, the semi-tropical 

 elements increase in number and the Kiusiu fauna is less char- 

 acteristically Japanese, having much in common with the neigh- 

 boring shores of China, while some of the species range north- 

 ward from India and Java. But these faunal districts have 

 no sharp barriers. Northern fishes t unquestionably of Alaskan 

 origin range as far south as Nagasaki, while certain semi-tropical 

 types extend their range northward to Hakodate and Volcano 

 Bay. The Inland Sea, which in a sense bounds the southern 

 fauna, serves at the same time as a means of its extension. While 

 each species has a fairly definite northern or southern limit, the 

 boundaries of a faunal district as a whole must be stated in the 

 most general terms. 



The well-known boundary called Blackiston's Line, which 

 passes through the Straits of Tsugaru, between the two great 

 islands of Hondo and Hokkaido, marks the northern boundary 

 of monkeys, pheasants, and most tropical and semi-tropical birds 

 and mammals of Japan. But as to the fishes, either marine or 

 fresh water, this line has no significance. The northern fresh- 

 water species probably readily cross it; the southern rarely 

 reach it. 



We may define as a fourth faunal area that of the Kuro 



* Formerly, but no longer, called Yeso in Japan. 



t Called Nippon on foreign maps, but not so in Japan, where Nippon means 

 the whole empire. 



$ Pleuronichthys cornutus, Hexagrammos otakii, etc. 



As Halichceres, Tetrapturus, Callionymus, Ariscopus, etc. 



