In the great basins and hollows from Rugen to the Gulfs of Bothnia and Finland the upper layers of water, from 30 to 70 metres (16 to 38 fathoms) in thickness, have almost the same salinity throughout.
It predominates along the Ligurian Riviera from Bordighera to Spezia, and on the Adriatic, near San Benedetto del Tronto and Gargano, and, crossing the Italian shore of the Ioian Sea, prevails in some regions of Calabria, and terminates around the gulfs of Salerno, Sorrento and Naples.
Where the great continental sag sinks below the ocean level, we have our gulfs and our Mediterraneans, seen in our type continent, as the Mexican Gulf and Hudson Bay.
It is situated on the isthmus between the gulfs of S Eufemia and of Squillace, the narrowest part of Calabria, 970 ft.
The Baltic, with the Gulfs of Bothnia and Finland, limits it on the N.W.; and two sinuous lines of land frontier separate it respectively from Sweden and Norway on the N.W.