The value of conch pearls is as variable as their form, color, and size, and they are sold by the fishermen at prices ranging from twenty-five cents to one dollar or more each. Those weighing from three to ten grains, and of good color and luster, but not quite regular in form, sell for about $10 per grain; those of exceptional perfection in color and form, and of about the same weights, sell for from $15 to $30 per grain. In other and exceptional cases, where the size is very large, the form perfect, and the color and luster choice, the value is enhanced to several hundred and even several thousand dollars each. A perfect conch pearl is among the most rare and most valuable of gems. An unusually choice one has sold in New York City for more than $5000. The yield fluctuates considerably, but perhaps averages about $85,000 in value annually. One of the finest conch pearls ever found is shown on the plate with the conch shell. There are two important materials that have occasionally been sold and mistaken for the conch pearl. First, the pale Italian, Japanese, or West Indian coral, with a color very closely approaching that of the pearl. By means of a lens it can readily be seen that the coral is in layers, and does not possess the concentric structure of the pearl, or the peculiar interwoven structure, with its characteristic sheen, so frequent in conch pearls. Secondly, the pink conch shell in which the pearl itself is found; this is frequently cut to imitate the pearl and sold as such in the West Indies and elsewhere. This can also be detected by the fact that the layers are almost horizontal and the structure is not concentric or interwoven, as it is in the conch pearl, while the luster is more like that of the shell than that of the pearly nacre. Streeter relates that many years ago an ingenious American turned out some bits of conch shell into the shape of pearls and placed them in the conch shells. A slight secretion formed over them, but it was not the true pearly secretion, and the layer was very thin, so that the deception was easily detected. Not the least interesting of the American pearl fisheries is that which has the abalones (Haliotis) for its object. These occur in many inshore tropical and semi-tropical waters, and particularly in the marginal waters of the Pacific. They attach themselves to the rocks by means of their large muscular disk-shaped foot, which acts like a sucker or an exhaust-cup.