Family Cerithiidae

Shell size to 25 mm; shell with sharp apex and nine to ten whorls. Nine to 11 nodulose axial ribs per whorl, crossed by spiral lines. Color light-tan to slate to light-brown covered with small brown specks that form spiral rows

Shell to 16 mm; sculpture nodulose sculpture, with about 3-4 spiral rows of beads. Color variable, brown, dark-brown, blackish, or mottled with white flecks. Aperture usually white inside. This is not a common species locally. The shell in the main illustration (BMSM 127415) was collected by Susan Hewitt on Turner Beach (Blind Pass), Captiva, in December 2018; the shell in the additional image is one of two found in December 2016 at Turner Beach by Susan J. Hewitt and Steve Rosenthal.

Shell size to 25 mm; shell sculptured with numerous spiral threads a spiral row of of a about 10 minute tubercles below suture. Color white with darker spots arranged in spiral lines. A shallow species, in sand and sea grass beds. Not common in area. This juvenile specimen was collected on Sanibel.

Cerithium atratum (Born, 1778) is the most common among the six species of the family Cerithiidae present on the barrier islands of Southwest Florida. Its shell grows to about 40 mm (about 1.5 inches) and bears a sculpture of spiral cords with numerous beads. Those spiral cords are separated by smaller spiral lines. The shell color is dirt-white to gray covered with irregular brown mottlings or specklings. This detritus-feeding species is very common in the shallow bay areas and sandy-muddy flats.

Shell size to 4 mm; shell with six to eight rounded whorls. Sculpture of spiral lines and weak axial ribs which intersect forming raised nodules. Body whorl usually with varix. Inner lip squarish. Color extremely variable, usually light- to dark-brown, sometimes with darker mottlings or specklings. Common in seagrass beds.