Strongly contrasting with the usually small land- and fresh-water turtles are the great sea-turtles, such as the leather-back, the loggerhead and the green turtles. Some of these animals reach a length of six feet and more and a weight of nine hundred pounds, and have the feet compressed and fin-shaped for swimming. They live in the open ocean, coming on land only to lay their eggs, which are buried in the sand of ocean islands. These egg-laying visits are almost always made at night, and the turtles are then often caught by "turtlers." The flesh of most of the sea-turtles is used for food, and from the shell of certain species, notably the "hawk-bill" (_Eretmochelys imbricata_) the beautiful "tortoise-shell" used for making combs and other articles is obtained. The common green turtle (_Chelonia mydas_) of the Atlantic coast is the species most prized for food. It is a vegetarian, feeding on the roots of _Zostera_, the plant known in New England as eel-grass, though farther south it is called turtle-grass. When grazing the turtles eat only the roots, the tops thus rising to the surface, where they indicate to the turtler the animal's whereabouts. The turtler, armed with a strong steel barb attached to a rope and loosely fitted to the end of a pole, carefully rows up to the unsuspecting animal, and with a strong thrust plunges the barb through its shell, withdraws the pole, and, grasping the rope, now firmly attached to the turtle's back, lifts the animal to the surface. Here, with assistance, he turns it into the boat, where it is rendered helpless by being thrown on its back and by having its flippers tied. These turtles are also caught on their breeding-grounds, being found on the sand at night by the turtler, turned over on their backs, and left thus securely caught until assistance comes to help get them into the boats. =Snakes and lizards (Squamata).=--TECHNICAL NOTE.--A snake has already been dissected and studied. It will be instructive to compare the external structures, at least, of a lizard with that of the snake. Specimens of some species of the common swift (_Sceloporus_) are obtainable almost anywhere in the United States. The "pine-lizards" of the east belong to this genus. Lizards may be sought for in woods, along fences, and especially on warm rocks. [Illustration: FIG. 125.--The blue-tailed skink, _Eumeces skeltonianus_. (From living specimen.)]