PHYSICAL AND BIOLOGICAL CONDITIONS IN THE NORTH SEA. 25 



o 



Western Baltic. But it will be more instructive now to take the species 

 of the southern area in the divisions already distinguished, and 

 note which occur in the Western Baltic and which do not, and what 

 others occur in addition. This analysis has been made by Heincke. Of 

 the aperticolous southern species of the southern area of the North Sea, 

 all occur also in the Western Baltic. The mackerel, scad, and gar-fish 

 occur in some numbers, and are classed by Mobius and Heincke as con- 

 stant rarer residents, but are really summer immigrants making their 

 appearance in May, and absent after October or November. The hake 

 is a rare visitor, and has only been occasionally taken on the east coast 

 of Schleswig-Holstein in November and December. The tunny and 

 anchovy are also but occasional immigrants, which have been occasion- 

 ally taken in autumn. 



Of fundicolous forms, the following, according to Heincke, do not 

 occur in the Western Baltic : Zeus fciber, the Dory ; Callionymus lyra, 

 the Dragonet ; Gadus luscus, the Pout ; Motella tricin-ata, the Three- 

 bearded Kockling : Solea lutea, the Solenette ; Arnoglossus laterna, the 

 Scald-fish ; Galeus vulgaris, the Tope ; Mustclus vulgaris, the Smooth 

 Hound ; Scyllium canicula, the Small Spotted Dog-fish ; Amphioxus 

 lanccolatus, the Lancelet. 



All these species have, however, been found in more or less abundance 

 on the west and south coasts of Norway, with the exception of two, 

 Solca lutea, and Mustelus vulgaris. The latter has been taken at the 

 Shetlands and Orkneys. Of littoral species only two, Nerophis aequoreus 

 and Lahrus mixtus, are stated by Heincke to occur at Heligoland and 

 not in the Western Baltic, but these again are fairly common on 

 the south and west coasts of Norway, as far to the north as Tromso. 



On the other hand, the following southern species occur in the 

 Western Baltic, which are not found in the Heligoland Bight or the 

 southern part of the North Sea : — 



Aperticolous : Sciaena aquila ; Xiphias gladius ; Orthagoriscus 

 viola ; Carcharias glaucus. 



Fundicolous : Brama Rayi (deep sea) ; Gadus mimdus ; Raja 

 fullonica. 



Littoral: Gobius niger ; Lahrus maculatus; Crenilahrus mclops; 

 Nerophis ophidion. 



In addition to these a large number of southern species have been 

 taken more or less frequently on the west coast of Norway. Of pelagic 

 or aperticolous forms, Collett (JSforgcs Fiske, 1875 J gives Lampris luna; 

 Antcnnarius marmoratus ; Argyropclccus Olfersii ; Exococtus volitans ; 

 Alopecias vidpes ; ScojJelus caninianus ; Scomhresox saurus. 



These southern aperticolous forms found on the coast of Norway, and 

 not in the southern part of the North Sea, are oceanic species which live 



