The influence of the opposite conditions in reference to ocean currents experienced by the eastern and western borders of the continent are even more marked in the life of the adjacent waters than in the vegetation and fauna of the land itself. The plant and invertebrate life of the shoal waters of the Pacific coast, consisting largely of southern species, is exceedingly rich and varied, even to the inlets of the Alaska coast, where glaciers come down to the sea; while on the Atlantic border, northern species occur on the New England coast, and even farther south. The contrasts in temperature between the waters of the Atlantic and Pacific which cover the submerged border of the continent are well shown by the distribution of the cod, the most valuable of all fishes to man, which, as is well known, belongs to the northern fauna and ranges from the north Atlantic about the arctic coast of both the Old and the New Hemispheres, to the north Pacific. On the east coast of America this circumpolar fish, of which several species are known, is found occasionally as far south as Cape Hatteras, but the most southern "bank" on which it is extensively taken is off Cape Cod, in latitude 42 deg.; on the west coast it travels perhaps as far south as the mouth of the Columbia, but the most southern locality where it occurs in commercial quantities is off the Shumagin Islands, in latitude 55 deg.. The life of the continental shelf, as well as of the adjacent land, thus bears testimony to the vast importance to North America of the great ocean currents washing its shores.