THE PYRAMID SHELLS - OBELISK SHELLS - FAMILY PYRAMIDELLIDAE Shell slenderly spiral, of many whorls, coiled to the left; aperture entire; columella with one or more folds; operculum horny; foot extending far beyond head; proboscis long, retractile; radula wanting; tentacles flattened, ear-shaped, channeled outside.
This family includes but one genus in which living species exist. They are believed to be carnivorous, despite the deficient mouth parts.
Genus PYRAMIDELLA, Lam.
Characters of the family. Tropical seas.
The Obelisk Shell (P. conica, C. B. Ads.) is our represen tative of this genus. It occurs in Florida and at San Diego, Cal. Its ten flat whorls are separated by a deep spiral suture. It has a slender brownish spire half an inch high. Three folds are seen on the columella. This shell is rare.
Genus TURBONILLA, Leach Shell minute, awl-shaped, its many whorls crossed by sharp, close ridges, columella straight, outer lip thin, simple.
A very large genus of very small pyramid shells, widely distributed, chiefly in warm seas.
The Short Pyramid Shell (T. curia, DaII) is a Cerithium in form, but its daintily cross-ridged spire is but one-third of an inch long.
Habitat.— Cape Hatteras southward.
The Chestnut Turbonilla (T. castanea, Cpr.), with the 172 The Pyramid Shells. Obelisk Shells characteristic cross ridges on its ten flat whorls, is a rich brown on the outside. Length, inch. California.
Genus ODOSTOMIA, Flem.
Even smaller than the preceding genus, which it resembles in form, in most cases a trifle stouter and with a tooth-like fold, always, on the curved columella. Animal lives on slimy excreta of other mollusks, or on polyps and sponges of small size. The shells are white and lack cross-sculpture.
Massachusetts Bay to West Indies, West Florida.
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