A conchylia cup is an Ancient Roman glass cup type with a conical base and a slightly everted rim, made of transparent to slightly colored glass. Its distinguishing characteristics are stylized open mouthed fish with indented fins and curving tails, often made of translucent glass and applied wavy colored threads, and affixed to the outer surface of the cup to produce its three-dimensional aspect. The most common type appears to have stylized fish swimming to the left. These vases could be entirely free-blown or their cup shape mold-blown, and the fish, or other sea creatures, free-blown onto it.