Mollusks

The Cut-ribbed Ark

Capable of growing beyond 4 inches, the Cut-ribbed Ark, Anadara secticostata (Reeve, 1844), is the largest among the seven species of shallow-water Ark Clams (families Arcidae and Noetiidae) found on Sanibel and Captiva. The large, yet elegant, shell of the Cut-ribbed Ark has the sculpture of curved radial ribs that is typical of other members of the family. Among other features, a faint groove that splits each rib longitudinally (hence the “cut-ribbed” qualifier in the common name) separates th

The Smooth Atlantic Tegula

Although the Smooth Atlantic Tegula, Tegula fasciata (Born, 1778), may be commonly found in other parts of Florida and of the western Atlantic Ocean, it is rarely found on Sanibel. Its shell may be almost an inch long, with a depressed ("flattened") spire, smooth, and about six whorls (shell “turns”) in fully grown specimens. The shell base is smooth, with a deep umbilicus (the “hole” under the shell). The color in this species is extremely variable, with many combinations of mottled stripes, sp

The Cabrit Murex

Last week I covered the Rose Murex, Vokesimurex rubidus. This week I am presenting a close relative, the Cabrit Murex, Vokesimurex cabritii (Bernardi, 1859). A larger species, Cabrit Murexes can reach about 2.5–3 inches in size. It differs from its “cousin”, the Rose Murex, by having cream or yellowish color and shorter spire (the part of the shell with many whorls, away from the opening, or aperture). As it happens with Rose Murexes, Cabrit Murex shells found on the beach or in shell piles afte

The Rose Murex

The family Muricidae of marine snails include some locally well-known and iconic species such as the Lace Murex, Apple Murex, and Cabrit Murex. A relatively uncommon member of the family, the Rose Murex, Vokesimurex rubidus (F.C. Baker, 1897) can typically be separated from its closer relatives by its coloration of pink or dark-pink spiral bands. The species is somewhat similar to Cabrit Murex, having comparable rows of shell spines, but is smaller, reaching less than two inches, has a relativel

The Angel Risso

At only 6 mm (about ¼ inch), the Angel Risso, Rissoina angeli Espinosa & Ortea, 2002, is another member of the rich micromollusk fauna found in the shallow waters of the barrier islands of Southwest Florida. Its shell is distinctive, with an elongate-conical shape, and a fine sculpture of 25 large ribs per whorl and finer spiral threads that do not cross those ribs (you will need a strong magnifying glass small microscope to be able to see the delicate microsculpture on this shell). The color i

The Emerson Miniature Cerith

Emerson Miniature Cerith, Retilaskeya emersoni (C.B. Adams, 1839) is one of those shells that could compete for the throne of “most handsome” local shell, if only it were five times larger than its actual size! But at 8 mm (0.3 inch) in average size, these Miniature Ceriths go unnoticed by most except for the serious microshell collectors. The species boasts an elegant sculpture of three tows of rounded, sometimes glossy beads, with the shell whorls separated by a well-defined groove (known as s

The Amber Glassy Bubble

The Amber Glassy Bubble, Haminoea succinea (Conrad, 1846) has a very thin, glass-like shell. It belongs in the same Glassy Bubble Genus, Haminoea, as the Antilles Glassy Bubble, a species covered in this column a couple of years ago. Live glassy bubbles can be seen, sometimes in large numbers, in the bays and protected seagrass flats of Southwest Florida, in particular during the Spring. Glassy bubbles completely envelop their shells with their bodies. The different species are all simultaneous

The Florida Caecum

These two pictures show the same shell, the Florida Caecum, Caecum floridanum Stimpson, 1851, a tiny gastropod not uncommon on the sandy beaches of SW Florida and that measures no more than 4 mm (a tad beyond 1/8 inch). The genus name Caecum means “blind” in Latin, and the word is also used for any structure that ends in a blind tube or pouch. The photo on top was taken under a standard microscope, and the one on the bottom with a scanning electron microscope (SEM), a sophisticated piece of equi

The Ravenel Scallop

The Ravenel Scallop, Euvola raveneli (Dall, 1898) is one of the most elusive among the local Scallop species. It is certainly the rarest of all shallow-water Scallop species occurring in Southwest Florida (excluding the Lions Paw, Nodipecten nodosus (Linnaeus, 1758), which lives in slightly deeper water). The Ravenel Scallop can be readily distinguished from the similar and relatively more common Ziczac Scallop, Euvola ziczac (Linnaeus, 1758), by the "split" or "double" radial ribs on the right

The Miniature Moon Snail

The Miniature Moon Snail, Tectonatica pusilla (Say, 1822) is a member of the Moon Snail family Naticidae, which includes the locally common Shark Eyes (two species) , and the not-so-common, but not too rare, Colorful Moon Snail. Miniature Moon Snails are also found locally, but are much rarer than those other members of the Naticidae family. They are also much smaller, with adult shells reaching only about 8 mm (about 1/3 inch). The shells have a color pattern of pale, wavy lines that is more pr