The food of the Thalassians consists principally of marine plants ; but it appears that some of them, especially those which exhale a musky odour, Chelonia Caouana (Cot:mane, Gray), for instance, feed also on crustaceans and many species of mollusks, the cuttles especi ally. Their jaws are robust, like the beaks of birds of prey ; solidly articulated and worked with highly developed muscles; and their horny beak, hooked above and below, is trenchant on the edges, and most frequently serrated, so as to assist in securing a slippery prey.
Whilst little is kn n with regard to the conduct of the two sexes during the breeding season, those attending the deposit of the eggs are better known. To reach the destined spot, the females have often to traverse the sea for more than fifty leagues, and the males accompany them to the sandy beaches of those desert islands selected for the places of nidification. Arrived at the end of their voyage, they timidly come forth from the sea after sunset; and as it is necessary to leave the eggs above high-water mark, they have often to drag themselves to a considerable distance before they can hollow out their nests (about two feet in diameter) during the night, and there lay at one sitting to the number of a hundred eggs. This laying is repeated thrice, at intervals of two or three weeks. The eggs vary in size, but are spherical, like tennis-balls ; and when they are laid, their investing membrane is slightly flexible, although covered with a delicate cal careous layer. After slightly covering the nest with light sand, the parent returns to the sea, leaving the eggs to the fostering influence of R tropical sun. The eggs are said to be hatched from the 15th to the 29th day; and when the young turtles come out, their shells are not yet formed, and they are white as if blanched. They instinctively make for the sea ; but on their road, and as they pause before entering the water, the birds of prey that have been watching for the moment of their appearance hasten to devour them ; whilst those that have escaped their terrestrial persecutors by getting into the sea, have to encounter a boat of voracious fishes and legions of ambushed crocodiles.
Those that escape attain, under favourable circumstances, enormous dimensions. Individuals of the genus Spharyis have been known to
weigh from 1500 lbs. to 1600 lbs. ; and some whose carapace has measured in its circumference more than 15 feet, and near 7 feet in length, have weighed down more than from 180016s. to 1900 lbs. Aged turtles often carry about with them on their carapace a little world of parasites, such as Ilustrer, Serptder, Balani, and Coronula whilst certain A nnelides securely fix themselves at the origin or base of the limbs, where the motion of the turtle cannot displace them.
Though many of the other Cholonia are highly useful to man, espe cially as articles of food, none are of such great utility as the Thalas shine. The advantages to be derived from them were not lost upon the ancients; and though Mercury is said to have taken the first hint for the structure of a lyre from the dried carapace and tendons of a tortoise (a Cymehpris, probably), found by the god after an inundation of the Nile, and which sounded when he struck ' the chortled the !benefits arising from the Thalassians are, if not so refined, of a much more substantial and varied nature. The inhabitants of those countries where the turtles grow to a large size do not merely derive from them a supply of food, but they convert their carapaces into boats, into huts, into drinking-troughs for their domestic animals, and baths for their children. The Chdonophagi of old, who inhabited the shores of India and the Red Sea, converted the enormous shells C. imbricata, the Hawk's-Bill Turtle of Catesby and Brown (Caretta imbricata, Gray; Test udo imbricata Linuams). Flesh bad. Eggs very good.
Sub-Genus 3.—Chelondes Caouanes: Logger-Head Turtles. Plates of the carapace not imbricated. Fifteen plates on the disc. Jaws slightly curved towards each other at their extremity.
C. Caouana, the Logger-Head Turtle of Catesby (Caouana Caretta, Gray); C. Dussuinierii (Chelbnla olivacea of Eschscholtz ; Caouana olivacea, Gray).
Sphargie, Merrem (Coriudo, Flem. ; Dermatochdys, Blainv.).—Body enveloped in a coriaceous hide, tuberculous in young subjects, com pletely smooth iu adults. Feet without nails.
S. corigcea (Teetudo Lyra, Donnd. and Bechst. ; Tortue Luth of the French; Coriaceous Tortoise of Pennant).