'Cameo conch' definitions:

Definition of 'Cameo conch'

From: GCIDE

Cameo \Cam"e*o\ (k[a^]m"[-e]*[-o]), n.; pl. Cameos (k[a^]m"[-e]*[=o]z). [It. cammeo; akin to F. cam['e]e, cama["i]eu, Sp. camafeo, LL. camaeus, camahutus; of unknown origin.] A carving in relief, esp. one on a small scale used as a jewel for personal adornment, or like. [1913 Webster +PJC]
Note: Most cameos are carved in a material which has layers of different colors, such stones as the onyx and sardonyx, and various kinds of shells, being used. The classical cameos made in Italy are carved on a seashell (see cameo conch, below), having an olive figure carved from the inner layer of the shell in relief on the white background of the outer layer of the shell. [1913 Webster]
Cameo conch (Zool.), a large, marine, univalve shell, esp. Cassis cameo, Cassis rua, and allied species, used for cutting cameos. See Quern conch. [1913 Webster]