Mollusks

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The Antillean Sphenia

The Antillean Sphenia, Sphenia fragilis (H. Adams & A. Adams, 1854) is a locally uncommon species of bivalve that reaches a little less than a half-inch in size. The shell is roughly rectangular, very thin and brittle, and chalky-white, with a very thin, yellowish-brown periostracus (the organic outer shell layers). In some cases, the shell extends posteriorly to form an elongate siphonal tube that may be as long as the rest of the shell; this tube is reinforced by a thicker periostracum. Spheni

The Yellow Egg Cockle

The Yellow Egg Cockle, Laevicardium mortoni (Conrad, 1830) is the last of eight locally found species of the bivalve family Cardiidae (Cockles) covered in this column. The Yellow Egg Cockle has a smooth shell, roughly circular in shape, with a strong “ridge” on its posterior end. It measures up to an inch in size, and usually displays a color pattern with typical purple-brown zigzag or “serrated” lines set on a cream background. The internal surface of the shell is cream or yellow and shows the

The Yellow Prickly Cockle

The Yellow Prickly Cockle, Dallocardia muricata (Linnaeus, 1758) is one of eight locally found species of the bivalve family Cardiidae. Its shells are roughly circular, measure up to 1.5–2 inches in length, and bear a number of radial ribs, each rib displaying a large number of small scales. This feature is shared with another, closely related local species, the Florida Prickly Cockle. This latter bivalve, however, has a more elongate shell, with colors ranging from white to pinkish-purple, whil

The Antillean Tusk Shell

Tusk shells belong in the molluscan class Scaphopoda, and are so named because they resemble small elephant tusks. The Antillean Tusk Shell, Antalis antillaris (d’Orbigny, 1853) is one of several local members of the family Dentaliidae. Its shell reaches about a half-inch in length, and is ornamented by longitudinal ridges, which are separated by grooves containing translucent “windows” of thinner shell material of unknown function. The local tusk shells are being studied by Shell Museum’s marin

The Ladder Horn Snail

The Ladder Horn Snail, Cerithideopsis scalariformis (Say, 1825), is one of two local members of the family Potamididae. Its shell reaches about one inch in length, and is ornamented by a sculpture of 20–26 slanted, axial ribs per whorl. The ribs stop abruptly at a single, well-defined spiral cord located at the shell suture (line separating two adjacent whorls). The shell lip is typically white with two or three brown bands anteriorly (closer to the shell base). This species inhabits back-bay ar

The Brown-line Niso

This shell of the Brown-line Niso, Niso aeglees Bush, 1885, is, so far, a one-of-a-kind find for the islands of Sanibel and Captiva (see below). This conical shell measures about 10 mm (about 0.4 inch), and is usually smooth or glossy, presenting no sculpture or ornamentations. Its color is whitish, with a thin red-brown band just above suture (groove separating two adjacent whorls). The species is known to occur in deeper water in the Gulf of Mexico, but this shell was found by Steve Rosenthal

The Gem Cyclostreme

At about 3.5 mm (about 1/8 inch) in size, the Gem Cyclostreme, Arene tricarinata (Stearns, 1872) is one of the small gastropods found along the shores of the Southwest Florida. The species is one of the smallest members of the family Areneidae, a group of mollusks present in the world’s tropical and subtropical seas. The ending of the species name, tricarinata, derives from the Latin for “three-keeled,” an allusion to the spiral ridges present on the periphery (outer edge) of the shell. The Gem

The Pennsylvania Lucine

The Pennsylvania Lucine, Lucina pensylvanica (Linnaeus, 1758) is relatively common on the eastern coast of Florida, but no so common along the shores of the Southwest Florida. The shell of this member of the family Lucinidae may reach 2 inches in length. It is circular, with marked, irregularly distributed commarginal (“concentric”) growth lines and a strong posterior groove. The color is dirt-white, sometimes with hints of light brown imparted by the delicate periostracum. Its periostracum cons

The West Indian False Cerith

The West Indian False Cerith, Lampanella minima (Gmelin, 1791), is the only representative of the gastropod family Batillariidae in Florida. (The species was, until recently, included in the genus Batillaria.) This species, which may reach a little tad under an inch in length, is extremely abundant in and around the intertidal (“between tide lines”) and supralittoral (“above the high tide line”) zones of mangroves in South and Southwest Florida. Populations of the species may form large aggregat

The Atlantic Fat Tellin

The Atlantic Fat Tellin, Leporimetis intastriata (Say, 1827), belongs to the Tellinidae, a family of bivalves that includes many species worldwide, and with at least 15 species locally. Fat Tellins are relatively large, reaching about 3 inches in length. They share the “curved” profile characteristic of members of the family, with the left valve slightly concave and the right one convex (This is shown in the bottom image, where the left valve is below the right one). In addition, the right valve