[There has been much confusion in the generic nomenclature of this family. The old name /Natica/ once did service for all the species; then the names /Lunatia/, /Neverita/, and /Polynices/ were applied to certain special forms; but it has been wisely proposed by conchologists to use the name /Natica/ for those forms having a shelly operculum, and to adopt the name /Polynices/ for those having a corneous operculum. /Lunatia/ and /Neverita/ have become subgenera of /Polynices/.] [pg369] GENUS ^Sigaretus^ A very interesting species of this genus occurs on the east coast, sparingly in New Jersey, but very abundantly south of Hatteras. /Sigaretus/ is a modified /Natica/. The spire is flattened and minute. The body-whorl, being greatly expanded, gives a wide, flaring, oblique aperture. The shell is ear-shaped and white, with fine revolving lines. There is no umbilicus. The operculum is small and rudimentary. The animal is large, with an enormous foot and greatly developed propodium, and is a sand-dweller. The common east-coast form is ^S. perspectivus^. (Plate LXVIII.) FAMILY ~CAPULIDÆ~ GENUS ^Crepidula^ [Illustration: /Crepidula fornicata./] ^C. fornicata.^ All collectors of mollusks on the Atlantic coast sooner or later encounter this exceedingly common species adhering to oyster-shells or scallops, and often to other large live shells. It is cast upon the beach along the entire length of the Atlantic coast. The shell is obliquely oval, dull whitish in color, and either smooth or rough or even ribbed, according to the nature of the surface to which it clings. The spire is almost entirely suppressed, the little inconspicuous apex being turned to one side and closely pressed down against the body of the shell. When looking into the interior of the shell one is reminded of a boat, for the upper portion of the aperture is covered by a horizontal shelly partition, called the diaphragm, a space being left below which would correspond to the forecastle of a ship. The "stern" is round, and the "bow" is suggestively pointed. [Illustration: /Crepidula plana./] ^C. plana.^ In this species the shell is white and flat, or slightly concave. Although it is pointed at the "bow" end and square at the "stern," the nautical resemblance stops there, because, being flat, there are no swelling sides and bow. The diaphragm is about one half the length of the shell, convex, shining, white, and translucent. /C. plana/ lives generally within the aperture of large dead shells. It has a wide range, from Maine to Florida. ^C. aculeata.^ A common Floridian species which has a remarkable range, being found in nearly all the tropical and semi-tropical waters of the world. It is smaller than /C. fornicata/, is reddish-brown with a white diaphragm, and has several radiating ribs on the back, which are inclined to be nodulous. (Plate LXVIII.) [pg370]