=Tortoise Shell.=--The following interesting account of the tortoise-shell industry is taken from Nature: The tortoise shell of commerce is obtained from the horny superficial plates overlying the bony case of the great majority of tortoises and turtles. Turtles differ from tortoises in the heart-shaped form of the upper half of the shell, and the conversion of the limbs into paddles adapted for swimming. The upper part of the shell carries a median row of five large superficial horny plates, flanked on either side by a row of four or five still larger flat plates; these thirteen or fifteen large plates affording some of the most valuable commercial tortoise shell in the particular species whose shell is in most demand. On the front and hind edges of the upper bony shell and the portion connecting the latter with the plastron, or lower shell, are a series of smaller horny plates, generally twenty-four in number, which are sharply bent in the middle and are known in the trade as "hoof." The under surface of the shell of a turtle carries six pairs of large, more or less flat, horny plates, for which the trade term, derived from their uniform color, is "yellow belly." In value they sometimes exceed all but the very finest of the large upper plates, generally known simply as "shell." Of the host of land and fresh-water tortoises, most of which are of comparatively small size, the horny plates (which, by the way, are altogether wanting in the so-called soft tortoises of tropical rivers), on account of their thinness and opacity, are now of no commercial value, at least in England. Moreover, it is by no means all species of marine turtles which yield commercial tortoise shell. Of these marine turtles, exclusive of the great leathery turtle, there are three well-marked and perfectly distinct types, severally represented by the green or edible turtle, the hawksbill, and the loggerhead. The hawksbill furnishes the most valuable shell. The largest and best plates, which are in the middle of the back, are about a quarter of an inch thick in the center, and measure about thirteen by eight inches, their weight being from about half a pound each to as much as one pound. The length of the carapace (the upper shell) in the hawksbill is about forty-two inches. It is found in all tropical and subtropical seas. From a dead turtle the plates of tortoise shell can be readily detached by beating. The highest price realized during 1898 in the London market was about 112_s._ 6_d._ (about $28) a pound for the very best selected shell. It is stated that 76,760 pounds of hawksbill shell were sold in London in 1898. The shell is very readily workable, being made partially plastic by immersion in hot water.