200 CASSIDID A. 
Animal with large head, and eyes at the exterior base of the 
tentacles, proboscis cylindrical, extensible, mantle and foot large. 
Operculum corneous, oval or oblong. 
The Cassides are active and voracious, living in sandy locali- 
ties and preying upon bivalve mollusks. 
Cassis, Lamarck. 
Syn.—Cassidea, Brug. Goniogalea, Morch. Galeodaria, Conr. 
Disir.—37 sp Tropical ; West Indies, Mediterranean, Africa, 
China, Japan, Australia. Fossil, 36 sp. Eocene—; Chili, France. 
OM Madagascariensis, Lam. (Ixii, 22) 
Shell solid, thick, with the last whorl very large, varicose ; 
aperture longitudinal, narrow, outer lip with a thickened, reflected 
margin, and dentate within, inner lip rugosely plicate. Oper- 
culum oval, narrow, with median apex (Ixii, 28). 
These shells are well adapted for cameo-cutting, from their 
substance being made up of differently-colored layers, and also 
from a difference of hardness and texture in the various layers, 
some approaching more nearly to the nature of nacreous than of 
porcellanous material. 
The word cameo, derived from the Arab word, signifying bas- 
relief, was originally restricted to hard stones, such as onyx, 
sardonyx, etc., engraved in relief; but the name has since been 
extended to gems cut on shell, lava, and other substances. 
In cameos the central layer forms the body of the relief, the 
inner layer being the ground, and the outer the third or super- 
ficial color, which is sometimes used to give a varied appearance 
to the surface of the figure. 
Shell-cameos, some years ago, were a good deal in fashion ; 
and even now a well-executed, artistic Roman shell-cameo is an 
elegant piece of art. Genoa and Rome are the seats of the best 
work, although many common ones are cut in France. In Rome 
there are about eighty shell-cameo cutters, and in Genoa thirty, 
some of whom also carve in coral. The art of cameo-cutting 
was confined to Rome for upward of forty years, and to Italy 
until the last twenty-six years, at which time an Italian began 
cutting cameos in Paris, and now over 3000 persons are 
employ ed in that city. e 
The black helmet (Cassis Madagascariensis), on account of 
the advantageous contrast of colors in the layers, produces 
very effective cameos, the carved figure of the white upper layer 
being strongly relieved by the dark, almost black, ground sup- 
plied by the second layer. 
The shell is first cut into pieces the size of the required 
cameos, by means of diamond dust and the slitting mill, or by 
a blade of steel fed with emery and water. It is then carefully 
shaped into a square, oval or other form on the grindstone, and 
