The Turtles or Sea Tortoises are distinguished from all others by a comparatively flat carapace, long members, the extremities of which terminate in broad paddles, the anterior much longer than the posterior ones; the toes, though formed of distinct pieces, can only act together, thus constituting true oars, admirably arranged for swimming. Their carapace, besides being flat, is indented and elongated in front, and contracted behind, being disposed in such a manner that the head and feet can be completely hidden. Marine Tortoises are the largest of their species: they swim and dive with great facility, and can remain long under water. The external orifice of the nasal canal is furnished with a sort of valve, which the animal raises when it is in the air and closes when under water; but it rarely leaves its liquid element except in the breeding season, when nature prompts it to seek the shore to lay its eggs. Some of the species, however, seek the shore in the night, when they frequent the banks of desert and solitary isles, where they browse on marine plants. Although they walk with difficulty, and even with pain, in quiet seas they may be seen floating like a boat, in absolute immobility, and asleep on the surface of the water. With their horny jaws, which are hard and trenchant as the beak of a bird of prey, some of them feed upon sea-weed and algæ, while others feed on living animals, such as crustaceans, zoophytes, and mollusks. We have seen how regularly and systematically the Land Tortoises proceed in depositing their eggs--nor is less precaution taken by the Sea Tortoise. The females, accompanied by the males, traverse several hundreds of miles of sea in order to deposit their eggs in some favoured locality. Other females resort, year after year, almost to a day, to the sandy shore of some desert isle, where they drag themselves ashore during the night, sufficiently inland to be safe from the tide. In some such spot, using their hind feet by way of a shovel, they excavate holes about thirty inches deep. Here they lay frequently a hundred eggs, covering them up afterwards with the fine sand, levelling the surface, and then returning to sea, leaving the eggs to be hatched by the solar rays. The eggs are round, slightly depressed at both ends, and furnished with a coriaceous shell. From the high temperature communicated to the sand-bank, they are hatched in about fifteen days. The females seem to have two or three layings in the season, at intervals of two or three weeks. When the young Turtles are hatched, they are feeble, white, and about the size of frogs, and their instincts lead them at once to the sea. Under the fostering care of their mother, those which have escaped the birds of prey on their way to the sea, and the fishes lying in wait for them, rapidly develop, and attain, under favourable circumstances, an enormous size,--some of the _Sphargis_, or Soft Turtles, having been