A Beginner's Guide to Shells
Credit: Jean Allsopp
Limpets & Keyhole Limpets
Approximately 35 species of Limpets live in North American waters. Conical shells may be smooth or ribbed, round or narrow at the base, and may reach 4 inches in diameter. Limpets living in turbulent wave areas have lower shell heights than those in calmer conditions. Limpets living among grasses have longer, narrower shells. Keyhole limpets have a hole or slit near the apex of their conical shell that sets them apart from true limpets.
Look for a rounded aperture on these shells, which range in height from one inch to 4 5/8 inches. They are slender, variably sculptured, have convex whorls, and are almost always white in color. Some 95 species inhabit North American coasts.
About 140 species of Murex live in North America. Most have spines or ribs and a lengthened canal on one end. The shells can be elongated or round in shape. They range in size from one inch to 10 inches high.
Eleven species of this mollusk are known to live in North American waters. Look for whorled shells with a short spire and a thick outer lip that can be either toothed or smooth.
Twenty-five species of Olive shells are found in North America. Look for various patterns and fine wrinkles, with a smooth and shiny exterior. Most are whorled and cylindrically elongated with a small spire. Olive shells may vary from 1 inch to 5 inches in length.
Nearly all of the 600 species of Cones around the world have a similar distinct design: a conical shape, flat top, and a slit-like lip running along its length. This shell's body can be smooth or angled with rounded or pointed knobs. Cones can range in height from one inch to 8 inches high.
These snail-like shells are common beachcombing finds on North American coasts. Moon shells vary in length from one inch to 5 inches. They're usually round, smooth and broad with short spires.
Tiny Periwinkles range from 1/8 inch to 1 inches high. The solidly built shells are smooth, sometimes sculpted, and round to oval in shape. Of the 23 species known in North American waters, almost all live in intertidal regions.
About 200 species of Whelks inhabit our waters from the arctic to the tropics. Whelks range in height from one inch to 8 inches. They may be smooth or have sculpturing lengthwise or spirally. Tropical species generally have thicker shells than their northern counterparts.
Most of the 25 North American Turbans favor warm waters. Look for thick shells with a pearly interior and either a smooth or sculpted exterior. Turbans range from 1/8 inch to 12 inches wide.
Approximately 180 species of Top shells inhabit North American waters. Look for spiral shells with variable exteriors and pearly-colored interiors. Top shells range in size from 1/8 inch to 6 inches in length.
There are only 20 species of volutes living in North America. Look for elongated shells that range from one inch to 18 inches high. A deepwater species within this group called junonia is prized for its brightly colored shell.
Turret or Screw Shells
There are 17 species of turret or screw shells inhabiting North American waters. These large shells are sized between one inch to 5 inches. Look for convex whorls and spiral coils, with a circular aperture.
All 70 known species of Conch inhabit tropical waters. Three of the seven species found in the tropical western Atlantic may be found as far north as Florida. Shells of the American species are 2 to 12 inches high and thick, with an extended outer lip. Look for a series of spines on the last two whorls near the spire.
Cowry shells are found in all tropical and warm waters, with six species living in the Caribbean, five in the southeast, and eight in western tropical waters. The cylindrical or oval shells range in size from 3/8 inch to 6 inches. Look for a smooth, shiny exterior with varied color patterns.
About 20 species of Auger live in North American waters. Look for whorled, narrow, and elongated shells with smooth or ribbed grooves on their exterior surface. Auger shells range anywhere from one inch to 8 7/8 inches high. The plate that seals the mouth of the shell is pointed at one end and rounded at the other.