_These animals are found in considerable numbers in the European seas._ By the ancients, cuttle-fish were in great esteem as a delicacy for the table; and, even at the present day, they are frequently eaten by the Italians, and by the inhabitants of other countries on the shores of the Mediterranean. There is, in the middle of their body, an oval bone, thick in the middle, and thin and sharp at the edges, light, spongy, and of whitish colour. These bones were formerly employed in medicine, and are still kept in the druggists' shops. When dried and pulverized, they are used by silversmiths as moulds, in which they cast spoons, rings, and other small work. When burnt or calcined, they are useful for the cleaning and polishing of silver and other hard substances, and sometimes for correcting the acidity of wines. The body of the cuttle-fish is furnished with a vessel that contains a considerable quantity of dark-coloured or inky fluid, which the animal emits into the water, to conceal its retreat when alarmed by the approach of its enemies. And it is generally supposed that the article called _Indian ink_ is this black fluid, in an inspissated or hardened state, and perfumed with musk and other substances. 272. _The PEARL-BEARING MYA_ (Mya margaritifera) _is a testaceous animal, having an oblong double or bivalve shell of somewhat oval shape, but narrower towards the middle than at the ends, and covered externally with a dark-coloured rough epidermis or skin, except on the protuberant parts near the hinge: one of the shells at the hinge has a single tooth or prominent part, which fits into a forked one in the other._ _The general depth of the shells is two inches, and breadth about five inches._ _Pearl-bearing myas are found in fresh-water rivers in many parts of Britain, and in those of most other countries within the arctic circle. The river Tay in Scotland, and the Conwy in Wales, are particularly noted for them._ In the river Tay some of these shells are found to contain good pearls; but fine ones are very scarce, and the greater part are of little or no value. They are of various shapes, round, oval, or elongated, and cylindrical, hemispherical, and resembling buttons. Several of the oblong ones have a contraction towards the middle, which gives them the appearance of two pearls joined together.