SEPIA (Gr. a iria, cuttlefish)  , a deep brown pigment obtained from the ink-sacs of various species of cuttlefish (q.v.) . To obtain sepia the ink-sac, immediately on the capture of the animal, is extracted from the body and speedily dried to prevent putrefaction . The contents are subsequently powdered, dissolved in caustic alkali, and precipitated from the solution by neutralizing with acid . The precipitate after washing with water is ready to make up into any form required for use . Sepia-bone or cuttle-bone consists of the internal " shell " or skeleton of Sepia officinalis and other allied species . It is an oblong convex structure from 4 to to in. in length and t to 3 in. in greatest width, consisting internally of a highly porous cellular mass of calcium carbonate with some animal matters covered by a hard thin glassy layer . It is used principally as a polishing material and for tooth powder, and also as a moulding material for fine castings in precious metals .