OIV THE FAUNA OF JAPAN. 127 



Shimane prefecture, 



A large number of molluscs are known from this district, of which 

 the most valuable species are (Mrea cjigas, 31actra sachalinensis, Pecten 

 yessoensis, Ommastrephes sloani pacificus, etc. The oyster attains a 

 large size, its famous natural bed being found in the lake of Saruma 

 in Hokkaido. On the shores of the northern islands as well as in 

 Aomori bay abounds the above named Pecten, which is of very large 

 size. The cuttlefish is of great commercial value, being caught in 

 great quantities to be consumed as food or used as bait. Besides, we 

 find that there appear in this district such squids as Gonotus fahricii 

 and G. magister. The former is limited in distribution to the north 

 of Hokkaido, while the latter comes down to as far south as Miyagi 

 and Shimane prefectures. The bays of Hokodate and Aomori are 

 famous for some species of branchiopods, like Terehratella coreamca, 

 etc. 



Extensively distributed here are numerous worms, such as IcJdkyo- 

 hdella uohir, Ich. vircjcda, etc. amongst leeches; Nereis ezoensis, Har- 

 mothoe yendoi, B. imhricoia, Polynoe gymnonoia, etc. amongst poly- 

 chaetes ; Dendrodoma blandion, Eclmirus pcdlasii, etc. among gephp-e- 

 ans. Of these some forms extend southwards down to the shores of 

 Shikoku and Kyushu. 



Amongst medusae, such forms as Haliclydus spp., Aurelia limhata, 

 Cyanea spp., Chrysaora spp., StauropJiora discoidea, and Sarsia spp. 

 frequent the northern waters. Spread into the middle zone are oftentimes 

 seen some species of a northern character, such as PhacellopJiora spp., 

 etc. Growing along the weed and on other objects are seen a number 

 of hydroids, such as Ehizocaulits verticiUatibS, Ohelia longissima, Gram- 

 maria scandens, and species of Halicium, AhiefAnaria, and Scdacia. 



The sponge fauna is comparatively poor, the notable species being 

 Chonelamia ccdyx, Jphroccdlutes vastus, etc. They are found to extend 

 south down to the Sagami Sea. 



Middle Zone. — In this district the arctic or subarctic overlaps 

 the tropical or subtropical fauna, there being distinguished a great 

 variety of animals. Most of the types characteristically Japanese belong 

 here, abounding in rock pools and about the rocky islands. Setting 

 asidesome mammals, northern and southern, some whalebone whales 

 may be recorded here, which are of great economic importance. The 

 blue whale (Balaenoptera sihlaldii) which is of wide distribution and 

 of migratory habits, appears off Kinkwasan and Hokkaido in summer, 



