Cuttle Fish (Sepia Officinalis), a molluscous animal or shellfish, of the family sepiadm and class cephalopoda. The shell, which characterizes the family, is a broad laminated plate imbedded in the back part of the mantle, and terminating behind in an imperfectly chambered apex (mucro), which is supposed to answer as a sort of fender in the collisions the animals are exposed to in swimming backward. This shell is a friable calcareous substance known as cuttle bone or pounce, and used for polishing soft metals. The bone of a Chinese cuttle fish has been found 1 1/2 ft long. As a fossil the bone has been met with in the eocene clays of the London basin, and of forms indicating extinct species. The cuttle fishes are provided with eight arms and two long tentacles, all of which radiate from around the head. The tentacles are provided with suckers, and reach beyond the arms to seize prey, and serve also to moor the animal. The suckers hold so fast to objects that the limb will part from the body before they let go. By means of their arms they walk on the bottom with their heads downward; the same organs aid them in swimming, and a propelling force is moreover obtained by violently ejecting water from their branchial chamber.
As a means of defence they are provided with an ink bag, the discharge of which opens into the funnel by which the water is ejected from the two gills; when attacked the animal instantly darkens the water with the black fluid from this bag, and retreats in the obscurity it occasions. Several species of sepia produce this inky substance. It was well known to the ancients, and is described by Aristotle. (See Sepia.) Cuttle fishes are found in the open sea in nearly all parts of the world; and they appear near the coasts periodically in shoals. They have large eyes on the sides of the head, which seem designed for use in the night or in the darkness of deep waters, as the animal avoids the light of the day. The cuttle fish attains a length of about 3 ft.
Sepia officinalis and Shell.