THE RICE SHELLS Genus OLIVELLA, Swains.
This genus is very small in number of species, and in size of the shells. These are cylindrical, produced into tapering spires; they have thin horny operculums. The mollusks live under the surface on sandy beaches. A lifted pellet of sand reveals their presence. They have no eyes, nor any need of them. The foot spreads into two lobes which envelope the shell. Thrown into the water, an Olivella uses these lobes as swimming organs, by which it speeds to cover. These shells are sold by the quart for use in "fancy work." The Little Olive (0. Inutica, Say), 1- inch long, or less, is a delicate thin spiral, tapering to both ends. Between the lower suture and a basal white band the body whorl is crossed by wavy lines or bands of chocolate on a pale, almost translucent ground. The aperture is half of the shell's total length.
Habitat.— North Carolina to West Indies.
95 The Olive Shells. Rice Shells. Harp Shells The San Pedro Rice Shell (0. Pedroana, Conr.) has a slim, shining little shell, coloured bluish or brown, and sometimes striped with yellow. It is about inch long. It lifts up a small pellet of sand, as if by thrusting up its head to see if the tide has gone away and left it. I have found them in plenty on San Pedro Bay, Cal.
The Twisted Olivella (0. intorta, Cpr.) is small, too, but stout in build compared with the last species. The pale surface is spirally striped with yellow. The suture is deep; the columella bears one fold, and spreads into a large callus above. The outer lip is thin and curved at the base.
Habitat.— California.
Genus ANCILLARIA, Lam.
Shell oliviform, of few coils, thin, polished; sutures filled with callus; lip flaring, frequently squared anteriorly; a strong spiral ridge ends in a tooth near base of body whorl; foot fissured, very large, reflected over shell; mantle prolonged in front into a long siphon; tentacles united to form veil; eyes wanting.
A small genus of seventeen species of active, gliding mol lusks, in tropical waters, chiefly East Indian.
The Cinnamon Ancillaria (A. cinnemomea, Lam.) is the type, though by no means as large as the largest species in the genus. The colour is cinnamon yellow, with two bands, brown and white, around the spire. The lining is a paler tint. The flaring lip has a squarish corner below. The white columella bears fine oblique striations. The revolving basal sulcus ends in a tooth on the lip. Length, to it inches.
Habitat.— Red Sea, Persian Gulf.
Habitat.— Madagascar, Australia.
The Polished Ancillaria (A. glabrata, Linn.) has a spire as long as the wide aperture. This handsome fusiform species is 96 The Olive Shells. Rice Shells. Harp Shells yellow and white and highly polished. The basal grooves lead to a deep umbilicus. Length, 2 to 3 inches. Habitat.— West Indies.