Page:The New International Encyclopædia 1st ed. v. 19.djvu/666

* TURRETIN. 574 TURTLE. (1711-37). Consult the lives of the elder and the younger Tnrretin, as they are commonly called, "by K. de 13ude (Lausanne, 1880). TURTLE (probably a corruption either of torloise. or of Sp. iurluga. Port., It. tartaruga, OF. tortuge. tortue, Fr. tvituc, tortoise; in either case ultimately from Lat. lortus, twisted, so called on account of the crooked feet; probably influenced by popular etymology with Eng. turtle, sort of dove). A shell-incased reptile of the order Chelonia. The word 'turtle' is used mainly to indicate the large marine forms, although in the United States it is applied freely to both fresh-water and land forms. 'Tortoise' (q.v.), strictly speaking, refers to land forms. Structure. The body of a turtle is invariably short and broad, and is protected both above and below by more or less bony shields, with spaces between" them in front and behind, into which the head and legs may be drawn. The conical tail is usually simply bent around against the side of the body when the turtle retracts into the shell, and thus covers the circular vent. The armature or 'shell' is composed of an upper part, the 'carapace,' and a lower, the 'plastron.' The carapace is formed from the ribs, of which there are eight pairs; and from the annular parts of the dorsal vertebra-, expanded into plates, which are joined to each other by dentilated sutures, so that the whole acquires great firmness, and the dorsal vertebrie are rendered immovable. The plastron is formed of pieces which represent the sternum or breast-bone, and which are ordinarily nine in number, and have names, as also have the parts of the carapace. The box-tortoise has cer- tain plates movable, so as more completely to in- close its body. The turtles and other aquatic chelonians cannot thus withdraw their head, tail, and limbs from danger, but the greater activity of their movements compensates for this. The above remarks apply to all turtles (Thecophora) except the leatherbacks (Atbecaj), whose body is jacketed in a continuous leather-like case com- posed largely of a mosaic of polygonal bony plates: and the vertebra; and ribs are not fused with, but are free from the carapace. See Leatheeb.ck. Externally the entire shell is covered with horny epidermal plates or shields of various forms and ornamentations, but arranged in all families on a regular plan. Each shield grows individually, the rings visible upon many of them indicating "each a year's growth — at least in countries where a winter hibernation and conse- quent suspension of growth takes place. These plates may be detached by heat, and in the hawksbill are of the beautiful material called 'tortoise-shell' (q.v.). The neck, legs, and tail are often provided with a horny scaled arma- ture. A cuticular layer covers the outside of the armature and i.s shed in fragments from time to time. The skull agrees fundamentally with that of crocodiles, but has several peculiar features, and is very solid. The mouth is bounded by a more or less horny beak like that of birds. The jaw is toothless, and the food is swallowed whole. There is, therefore, no need of a delicate sense of taste, and this sense is degenerate. In the stomach there are no organs of trituration, and the process of digestion is necessarily very slow, and is dependent on the action of the gas- tric juice. The heart is short, thick, and has but one ventricle. The lungs are large and are capa- ble of containing much air. The air is drawn into the mouth, the passages to the nares are tlien stopped by the tongue, and the air is gulped down. This way of getting air into the lungs ia required by the" rigidity of the armature, which prevents expansion and contraction of the chest. Turtles can remain under water for an hour or so without renewing the lung contents. The eye- sight of turtles is very keen. The eye is pro- tected by an upper and a lower . lid and in ad- dition by a nictitating membrane, as in birds. The sense of hearing is very acute. Habits and Habitat. When startled, some turtles, such as the wood-turtle, give a loud snake-like hiss. The males of the large Gala- pagos tortoises, according to Darwin, bellow or roar at the breeding season. Our conmion painted turtles utter a piping note, particularly in the spring. Turtles are diurnal except at the breeding season. With the exception of sea- turtles, the habitat of any individual turtle is very local. Certain tortoises and terrapins that have been marked have been observed in the same pasture year after year. Sea turtles return to the same locality to breed. Those in the tem- perate region hibernate throughout cold weather buried in earth or mud. Slarine forms have the legs modified into huge paddles, while amphil)ious forms have leg-like limbs only partially webbed. The coloration of those that spend considerable time on land simulates very much that of the ground. One form (see Matamata) has a fringed or foliaceous neck of much service in hid- ing it while seeking prey or avoiding foes. About 250 species of Chelonia are known, the most numerous species being found in fresh water, generally in warm climates. The marine species are the largest. Several kinds occur in the Alleghany region at considerable altitudes, but none live in the Rocky Moimtains. Chelonia are not numerous in kinds on the California coast, or in Europe, while on the Asiatic coast they are abundant. Food. Some of the sea-turtles, the land-tor- toises ( q.v. ), and a part of the fresh-water terra- pins (q.v.) are herbivorous, and these are the ones commonly eaten by man. Other sea and fresh-water forms feed entirely or in part on animal food, and are usually ferocious. Fresh- water forms, such as the snapping turtles ( q.v. ) , feed on fish, mussels, earthworms, insect larviB, young ducks, and the like. The box-turtle eats mushrooms and berries, and not infrequently makes raids on tomato gardens. Certain pond forms are practically omnivorous. Ego-Layino. Aquatic turtles come on land usually on moonlight nights at the breeding time to deposit their eggs. A sandy slope is preferred by most forms. In this soil they dig a hole with the hind feet, let the eggs fall within it. and re- place the sand so deftW that the ground seems scarcely disturbed. The female then retreats quickly to the water. Almost any soil will suf- fice for the American painted turtle, and the same rotten log may be utilized by many musk- turtles until it holds hundreds of eggs. The eggs, if not dug up by some animal, are left to hatch in the warm sand by the aid of the sun's heat alone. The snapping turtle deposits from IS to 30 eggs in the early morning hours. The wood, painted, and skunk'turtles, which lay from three