Turtle, the name popularly applied to the marine chelonian reptiles, equivalent to the suborder chelonii (Oppel), including the families sphargididoe and chelonioidoe; in these the dermal ossification is imperfect, and the limbs preserve through life the fingers undivided, as in the embryos of the higher families of the suborder amydoe or tortoises. For the characters of the order see Testudinata. The word turtle in Saxon meant turtle dove, a bird and not a reptile; and the English word had the same signification until the discovery of America, when sailors gave the name of turtle or turklo to the marine chelonians of the West Indies. As distinguished from the amydoe (see Toetoise), the turtles have the limbs converted into large, flattened, fin-like organs, the toes completely concealed by a common skin, the anterior pair always considerably longer than the posterior, and both frequently furnished with one or two nails on the outer margin, sometimes disappearing with age; the body is flattened to facilitate their progress through the water; swimming is performed almost entirely by the anterior limbs, the posterior moving independently and used chiefly to balance the body and guide it; the anterior are raised and depressed together very much like wings, and have a free sweep up and down and forward and backward; on land they move slowly and awkwardly by means of the front limbs, projecting them forward and dragging the body up to them, assisted greatly by the nails; the bulk of the body is forward, where are the principal muscular masses.
The head and limbs cannot be retracted under the shield as in the tortoises, and the plastron is less perfectly ossified and connected with the carapace; the ribs are narrowed toward the end, and the spaces between them at this point and the bony plates of the plastron are separated by intervals filled up by cartilage; the head is flattened above, protected by large plates; the jaws are strong and firmly articulated, horny, very sharp and beak-like, and the eyes large and prominent; the head is so placed on the neck as to allow the nostrils to be easily raised above the surface, their openings being closed by a fleshy valve. Much sea water is swallowed with their food, and when the former is of necessity regurgitated the latter is retained by the numerous horny processes, pointing backward, in the oesophagus. The very young are longer in proportion to their width, and grow broader. Though lower than the tortoises, the turtles exhibit features resembling those of birds in the form of the anterior limbs, the mode of locomotion, the preponderance of the fore part of the body, bill-like jaws, and overlapping epidermic appendages.
All are marine, excellent swimmers, and rarely approach the shore except to deposit their eggs; some feed entirely on sea weeds, but a few eat mollusks, crustaceans, and other aquatic animals; they are generally timid, and make but little resistance, though they are more bold and regardless of danger in the pairing season. The flesh of the herbivorous species is a wholesome food, and much sought after by epicures, while that of the carnivorous is disagreeable if not positively injurious; the callipee, or under part of the breast and abdomen, is considered the choicest part; the liver and fat are also much esteemed. They come on shore toward the end of spring to lay their eggs on the sandy beaches above high-water mark; they generally select desert islands or keys, and a still moonlight night; they dig a trench in the sand with their hind feet about 1½ ft. deep, and deposit therein about 100 eggs at each of three layings, with an interval of two or three weeks between them; the eggs are lightly covered with sand, and left to be hatched by the heat of the sun; if undisturbed, they return to the same shore year after year.
They are caught on the shore, and turned on their backs, a position from which they cannot escape, owing to the flatness and width of the shell; they are harpooned and taken in nets in the water, and in the Indian seas are captured by means of the remora. (See Sucking Fish.) - In the chelonioidoe the body is widest about midway, and the vertebral column descends continuously and gently to the tail; the shoulders and hind limbs are better protected than in the other family; the shield is more or less heart-shaped, with the posterior angle not prolonged into a point extending far over the tail; all the genera are represented on the coast of the United States, and are far less rapid swimmers than the sphargididce. The latter family has only the single genus sphargis (Merrem), showing well the inequality of the natural groups called families; the body is more conical than in the other turtles, the carapace leaving the hind legs as well as the shoulders and neck much exposed from its great contraction behind and in front; the lower parts are 'equally unprotected by the plastron, this with the carapace forming little more than a wide girdle around the thorax and abdomen; the skeleton is light, the paddles large and free, and everything seems arranged for rapid and long continued voyages. - The green turtle (chelonia midas, Schw.), sometimes attaining a length of 5 or 6 ft. and a weight of 5 or 6 owt., received its name from the color of the delicate fat which enriches the soup and other dishes of a course of turtle.
It has a short and rounded snout, and jaws acting like straight-edged shears cutting from behind forward, the upper slightly notched, the lower with a deeply serrated margin and a hook in front; shell smooth, with 13 plates, 5 vertebral and 8 lateral, not imbricated, slightly notched and serrated behind, and with 25 marginal plates; anterior limbs rounded at shoulder, covered with a tough skin and a few small plates; forearm and hand with large plates on the anterior border, smaller ones elsewhere, and an extensile fold of skin along the posterior margin; hind limbs short and flattened, covered with small plates and a larger fold of skin on the margin; a single nail to each limb; the shell is light brown, with darker lines and blotches, and sometimes with a greenish tinge; below pale yellowish white. It is abundant in the tropical waters of America, whence great numbers are carried alive to the northern states and to Europe; the West Indies are its headquarters, whence it wanders to the gulf of Mexico and the coasts of Guiana and Brazil; it is rarely found above lat. 34° N. on the Atlantic coast, and never on the shores of Europe; the Tortugas islands are a favorite resort.
It browses on the turtle grass (zostera marina), eating the succulent part nearest the root, the rest rising to the surface and disclosing the feeding grounds to the practised eye; in confinement it will eat and grow fat upon purslane (portulacca oleracea); numbers are kept for a long time in pens or crawls filled at every tide. It is often seen many hundred miles from land, and is easily taken when asleep on the surface; its capture gives employment to many and food to thousands in the West Indies. (For an account of other methods of taking them, and of the manner in which the eggs are laid, see Audubon's "Ornithological Biography," vol. ii., pp. 370-"T6, Boston, 1835.) During the actual laying of the eggs nothing can disturb their labors; they are hatched in eight or nine weeks. The flesh is exceedingly delicate, and wholesome in moderate quantities; the eggs of this and of all the species are also considered a delicacy. In the young the carapace is relatively narrrower, and the colors of the adults vary much.
As in all the species, the eggs are dropped one by one, and disposed in regular layers, during a period of about 20 minutes; they are round, 2 to 3 in. in diameter, with the external membrane flexible, very white, and containing a considerable quantity of calcareous matter; the shell of the young is soft, and affords but little protection. - The loggerhead turtle (thalassochelys caouana, Fitz.) has the body very wide across the shoulders; the head very large and flat, with wide mouth, the upper jaw nearly straight, and the lower hooked; shell smooth, with a keel along the median line, and a crescentic notch in the posterior border; the plates are thin and flexible, 5 vertebral and 10 lateral, not imbricated, and the marginal plates 25; each limb has two nails, corresponding to the first two fingers; the color above is light brown, sometimes with an olive tinge and often bordered with dirty yellowish; and the shield, as in the other turtles, is frequently more or less covered with barnacles, serpulae, and other parasites.
It has an extensive range on the American coast of the Atlantic, from Virginia to Brazil, and probably on the shores of Europe and in the Mediterranean; it is more common than the green turtle, and grows to 15 or 16 cwt.; it is voracious, feeding principally on mollusks, being able to crush with its powerful jaws the strongest shells; the flesh of the young is sometimes eaten, but that of the old is rank and tough; the scales are of little value, and even the eggs have a musky flavor; it is taken only for the considerable quantity of excellent burning oil which it furnishes. - The hawk's bill or imbricated turtle (eretmochelys imbricata, Fitz.) has a low and rather wide head, a long and narrow mouth, the upper jaw prolonged and hooked like the beak of a hawk, the lower jaw with a smaller hook, and both with serrated margins; the shell is slightly keeled, flattened and serrated behind, with five vertebral and eight lateral plates strongly imbricated or overlapping like the scales of a fish; the plastron has two keels, more or less worn off by age; there are two nails to each limb; anterior limbs verylong and wing-like; the head is protected by 14 scales; the tail is conical, not extending beyond the shell.
The color is yellowish above, marbled with rich chestnut brown, and yellowish white below; in the young there is a black spot on the four posterior pairs of plates. It is found in the West Indies, the gulf of Mexico, on the coasts of Guiana and Brazil, and has even strayed to the Mediterranean; the E. squamata (Ag.) is found in the Pacific and Indian oceans, the best being taken about the Moluccas and Papua. The food consists of sea weeds, crabs, mollusks, and fishes; in confinement it is fiercer than the preceding two; it rarely grows more than 3 ft. in length; its flesh is indifferent, and it is said unwholesome, though the eggs are good, and the species is sought after only for its beautiful horny plates, which constitute the tortoise shell of commerce. These are not considered of value unless from an animal weighing at least 160 lbs., as otherwise they are too thin; 15 lbs. of shell from a single one is a large amount, and yet in andmals of the same size the imbricated would be worth 10 times as much as the green turtle. Singapore and Canton are the great marts for tortoise shell.
It was consumed in large quantities in ancient Rome, even the door posts of the rich being inlaid with it; the carapace was used as a cradle and a bath tub for children, and as a shield for warriors. - The leathery or trunk turtle (sphargis coriacea, Merr.) is so named from having the carapace overlaid by a leathery skin instead of horny plates, smooth in the adult, but tuberculated in the young, and with seven longitudinal ridges; the head is large, narrowed in front of eyes, with small and circular nostrils, and large eyes with lids opening nearly vertically; jaws very strong and sharp-edged, the upper with three notches, the hook of the lower shutting into the central one; neck short and very thick; anterior limbs twice as long as the hind ones, the former falcate, the latter the widest; tail sharp, compressed on the sides, and not extending beyond the shell; the color is dark brown above, with lighter spots along the ridges. It is the largest of the turtles, attaining a length of 8 ft. and a weight of nearly a ton; its food consists of mollusks, crustaceans, fish, sea urchins, and marine plants; its flesh is of no value, but its shell has been used along the Mediterranean for making small boats, drinking troughs for animals, and children's bath tubs.
It is found on both sides of the Atlantic, especially in the tropics, coming north as far as Massachusetts bay, and following the Gulf stream across the Atlantic to the coasts of Europe and the Mediterranean; those of E. Asia and S. Africa may perhaps be a different species; none of this genus have nails on the limbs. It was known to the ancients. - The marine species have great tenacity of life under mutilation and deprivation of food. Turtles are found as far back as the Jurassic period, continued through the cretaceous, becoming more abundant and advancing further north than at the present day, though they were not so large as the existing species; in the limited strata of the eocene clay of the island of Sheppey more species have been discovered than now exist; large species have been found in the tertiary of South Carolina and the greensand of New Jersey, of several genera.
Green Turtle (Chelonia midas).
Hawk's Bill Turtle (Eretmochelys imbricata).
Trunk Turtle (Sphargis coriacea).