Though lessened in numbers and reduced in size, because the land has gradually won over to its side many sorts of animals which in former ages were exclusively confined to the water, and for other reasons, the sea still holds its share of every “branch” and “class” (except birds, and it may almost claim some of them, such as the albatross, penguins, and petrels), and a majority of the “orders” of animal life. Glance at the catalogue: Foraminifers, sponges, and polyps are chiefly confined to salt water; starfishes, urchins (or sea-eggs), and the like, wholly so: mollusks (next higher) are principally oceanic, and the majority of the crabs inhabit salt water. Among the last-named one species, the common horse-foot (_Limulus_) of our shores, remains as the solitary representative of that immense and varied group, the trilobites, which so crowded the Paleozoic sea-bottom that some rocks—for instance, the limestones of Iowa—are packed almost as full of their fossils as is a raisin-box of raisins. None of the insects is truly marine, yet some of them are seafaring, truly, for they spend their lives on drifting sea-wrack, or on beaches just out of reach of the tides; but most of the true worms are dwellers in the mud of sea-shores and sea-bottoms. No one knows of any land fishes; but I need not tell you that fishes throng in the fresh waters as well as in the salt, and that many species inhabit both at different seasons. In respect to the reptiles, of which the ancient oceans contained gigantic and horrid types, I do not know any now that are truly oceanic except the turtles, if you leave out the “sea-serpent,” of which we hear so many wonderful and not quite satisfactory tales. You will hear of “sea-snakes” in the East Indies, but they are only certain kinds of serpents which swim well, and pass the most of their time in the salt water, as several species of our own country do in the rivers and ponds; all the oriental sea-snakes are venomous. It is in this manner, too, that we may count certain birds, such as the petrels, auks, penguins, albatrosses, frigate-birds, and their kin, as belonging to the ocean. They spend all their life flying over the waves, seeking their food there, and some of them rarely go ashore, except to lay their eggs and hatch their young on remote rocks, resting and sleeping on the billows, when not busy at their hunting. In the highest rank of all, however, the mammals, several families are natives of the “great deep”—the whales, dolphins, and porpoises, the seals and walruses, and the manatees and dugongs. But all these must come to the surface to breathe, not having gills like fishes, but true lungs.