Curious Collectors of Clam Shells; Identification and Fun Facts
What is a Clam and Why should we Care?
First, we should care about clams because they have been an important part of Earth's ecosystem for at least 500 millions years as one of the first ever complex organisms, not to mention a delicious part of modern day cuisine.
Second, upon their death, they leave behind their hardened calcium carbonate remains and after millions of years their shells break up, get buried under layers of ocean bottom, then heat and pressure cement together with other sediments to form limestone, the building blocks for many a fine city building!
Third, their shells are amazing and beautiful to look at and admire. Human beings have found countless uses for their shells beginning from eons ago until modern times, but this could be another article entirely!
What is a clam and how do they live? Clam can be a term that covers all bivalves. Bivalves such as oysters and mussels attach themselves to hard objects, and scallops can free swim by flapping their valves together. Some clams bury themselves in wet sand and breathe by extending a tube to the surface. Those varieties usually possess a stronger foot for digging that looks like a tongue. Clams feed by filtering food particles such as algae and plankton from the water with their adapted gills, although the digging varieties extend their tubes to siphon food and oxygen. More primitive species used special tentacles. Bivalves lack a head or brain and usually have no eyes, although scallops are a notable exception. All bivalves possess a heart, kidneys, a mouth and anus, as well as a circulatory system.
Short video of clams burrowing
With the use of two abductor muscles clams can open and close their shells quite tightly. Very fittingly, the word “clam” gives rise to the metaphor “to clam up”, meaning to stop speaking or listening.
"Happy as a Clam" originally "Happy as a Clam in high water" began as a euphemism for a clam who was safe from predators, including humans, during high tide when it was too difficult to dig them up. The term has a long history, likely originating off the east coast of North America where clam hunting was and still is a popular pastime. In 1840, it was further popularized in a poem written by John G. Saxe, Sonnet to a Clam.
When identifying bivalves look for color, size, shape, number of ribs and the wings or ears that project at the hinge. So without further ado, time to get started identifying the clams I have in my generous collection, all of which are native to the Atlantic Coast of North America, west to the Gulf of Mexico and as far south as Brazil.
Cockles or Heart Shells
Cockles or Heart Shells of the U.S. Atlantic coast are close relatives to the edible cockles of Europe, although, there are approximately 250 species worldwide. They are known by shell collectors for their sturdy, heart-shaped shells when both valves are clamped together, and for their attractive appearance. Many cockles are taller that they are wide. They use a strong foot to burrow into the sand or propel themselves across it by pushing off and jumping several inches.
Atlantic Giant Cockle
Dinocardium robustum is a very beautiful bivalve, better known as the Atlantic Giant Cockle, or the Great Heart Cockle. Their shells are well inflated and large, up to 5 inches. They also have quite a sturdy shell with 32 to 36 radiating ribs and are commonly colored tan with reddish brown patches on their outer shells and a deep pinkish interior.
Range: Virginia, south to Florida, Gulf of Mexico, Texas and the Caribbean
Habitat: In mud or sandy shallows often in brackish inlets.
Yellow Prickly Cockle
The Yellow Prickly Cockle or Yellow Cockle, Trachycardium muricatum, is a small 2 inch (as adult), cheery round cockle with 20-40 radiating ribs. The ribs near the beak area are smooth; those farther out from the beak have small spines. The shell is yellowish-white with a delicate white to yellow tinted interior
Habitat: Moderate shallow water
Range: Native from North Carolina to Florida to West Indies, Brazil, and Texas
Florida Prickly Cockle
The Florida Prickly Cockle, Trachyardium egmontianum, is well inflated, medium sized up to 3 inches max with a white to tannish to light brown exterior and a salmon or pinkish color or sometimes purple interior. The 27-31 radial ribs on the outer shell are more scoop shaped than the Yellow Prickly Cockle.
Habitat: Gulf and bays. Sometimes found in seagrass beds although more common in south Texas
Range: North Carolina to Florida, and Texas
Egg Shell Cockle
The Egg (or Egg-Shell) Cockle, Laevicardium laevigatum, shells at first glance may be mistaken for an egg by its elongated oval shape and smooth surface. The shell is rather thin and inflated reaching up to 3 inches in length. Its fine radial ribs are delicately etched undetectable by touch, giving the shell's surface a smooth and polished appearance. The color is white, often tinged with brownish orange, yellow or a hint of purple, interior is white sometimes slightly tinged with pink.
A fun note about this mollusk is that it has the ability to jump rather well. A shell collector reported that a live specimen in his boat even leaped to its freedom.
Habitat: Shallow water sand or mud
Range: North Carolina to Florida and as far south as Brazil.
The name, "scallop," aptly describes the fluted edges of the animal's circular fan-shaped shell. Scallops otherwise known as "pectens" have rows of tiny eyes along the edge of the mantle making them unique among bivalves. They are jet-propelled. To explain, as their valves open, the space fills with water then the powerful muscle contracts and the valves pull shut shooting the water out sending the scallop forward rather rapidly. This large muscle is edible. They lack the stretchy foot for digging, unique from most bivalves. Scallops are more common along the Atlantic than on the Pacific shores.
Early Native American used scallop shells in their ceremonial dances and some tribes used them as ornaments.
Quick Moving Scallops Avoiding Predator
The Bay Scallop, Argopecten irradians, fan shaped exterior shell color ranges from bluish gray, purplish, to yellow, white, brown or reddish brown. The lower valve is commonly white and flatter. The interior of their valves are whitish, but often purplish near the hinge. They grow up to 4 inches maximum, but average 2 inches with fairly inflated upper valves. They have 19-21 ribs which are squarish compared to Calico Scallops and may be banded. The wings are fairly even, but may be worn off.
When bay scallops are young, they attach themselves to objects such as eelgrass. This helps them avoid bottom-feeding predators, such as sea stars. As bay scallops grow, they drop to the sediment surface and move on to tidal flats to feed at high tide. They are the most commonly edible shellfish.
Habitat: Subtidal zones, eelgrass beds, sandy and muddy bottoms, and offshore in shallow to moderately deep water, such as bays and harbors.
Range: Maine to Florida and Gulf of Mexico
A bit about the various color of same species shells
Some shells turn a variety of colors after they die. These colors depend on the shells afterlife environment. Black shells were likely darkened by iron sulfide if buried in sulfurous muck. Pink, rust or brown are colors most shells turn after decades of exposure to air and sun.
Florida White Scallops
The Florida White Scallops are bay scallops described above. One other feature about bay scallops is that their shells are not the most sturdy compared to the thick shells associated with cockles and especially the ark varieties described below. Their shells may be found with or without their wings.
Euvola ziczac, Zigzag Scallop, have varying colored rounded ribs from white to orange, yellow, gray and purple. The lower valve is somewhat cup-shaped, whereas the upper valve is fairly flat. The ear/wings are uneven. They exhibit a zigzag pattern (ENLARGE PHOTO) of tiny or distinct stripes on their outer shells which gives the name. They also move in a zigzag pattern when jetting. The interior valve is whitish and purple brown half way to the outer edge. They grow up to 4 inches
Habitat: Shallow waters near the shore and form beds in sandy areas
Range: North Carolina, throughout the Gulf of Mexico and the Caribbean, and as far south as Brazil.
Lions Paw Scallop - Nodipecten nodosus
Lions Paw Seashells, Nodipecten nodosus, formerly Lyropecten nodosus, differ from Nodipecten subnodosus. It is an ancestor to this Pacific species. It's also often confused with another Western Atlantic species, Nodipecten fragosus. Nodipecten nodosus does not have the tendency to develop nodes on the ribs like the species, Nodipecten fragosus. The right valve never shows nodes. The Lions Paw can be colored white, brown, reddish and sometimes mauve to purplish showing some spots. They have 9 -10 broad radiating deep ribs with additional fine lines. Look for the wide copper interior banding around the perimeter. Growth up to 4 inches.
Habitat: Fairly shallow water moderately exposed to sheltered reef systems, attached to corals and loose rubble
Range: Atlantic coast of North America, ranging from North Carolina to Florida, the West Indies, including Brazil and Bermuda.
The pretty Calico Scallop seashells, Argopecten gibbus, are a favorite with shell collectors striving to get the greatest variety of shadings. Some collectors have a hundred Calicos, all of different color combinations. Their mottled purple, orange, pink or even brown hued shells commonly wash ashore providing beach goers with colorful treasures. They're often found with their wings/ears broken off. They have 19-21 roundish ribs over their fairly dome shaped valves and grow to almost 3 inches maximum.
Habitat: Although closely related to bay scallops, calico scallops live in deeper, offshore waters. Calico scallops are found on sandy or shelly bottoms.
Range: Native from the coast of North Carolina to Florida, the Gulf of Mexico and the West Indies.
Checkerboard Clam or Calico Clam
Another popular shell among collectors, the Checkerboard Clam (also called Spotted Clam or Calico Clam), Macrocallista maculata, grows up to about 2 1/2 inches and is edible. It has an exterior of creamy white and checkerboard markings of brownish red with an interior of polished white with yellow or faint lavender markings. It has a moderately strong shell that is oval with very fine radial lines.
This Venus Shell is named for the Goddess Venus and is noted for its graceful lines and beauty of color and sculpture.
Habitat: Shallow sandy bottom waters
Range: North Carolina, Florida to the West Indies, Bermuda to Brazil
Sunray Venus Clam
Sunray Venus, Macrocallista nimbosa, has also been called Giant Callista. Average size is 3 inches; largest 5 inches and is edible. Violet gray to tanish with darker streaks radiating out from the hinge. Interior is dull white with a tinge of red over central area. Fresher specimens are more pinkish. It has an elongated oval shaped shell with a glossy, smooth surface. Native Americans used them as eating utensils.
Habitat: Sandy bottoms in shallow water
Range: Native to Florida West Coast, St. Petersburg to Marco, or beginning of the Everglades Islands. Also as far north as North Carolina and west to Texas.
Cross Barred Venus
The Cross Barred Venus, Chione cancellata, is a roundish triangular clam marked by distinct radiating and crossover lines, giving it a miniature lattice-work appearance. The slightly inflated shell is whitish often with brown markings. The inner surface of the shell also displays a pretty purple color. Gathering enough of the living clams can make a delicious chowder.
Habitat: More abundant in vegetative areas of bays
Range: North Carolina to Florida to the West Indies.
Princess Venus Clam
I love this little seashell for its deep brown color against its striking white interior, often with purplish stains. The Princess Venus Clam, Periglypta listeri, grows to only about 2 inches as adult, is heart shaped with numerous fine concentric rings and fine radial ribs on the exterior. It has a fairly inflated sturdy shell.
Habitat: Buries in gravel, sand and mud in mid-intertidal zones
Range: Florida to West Indies
Pronounced “Co-hog”, the Northern Quahog, Mercenaria mercenaria, is a large, thick, hard-shelled clam, also known as a type of Venus Clam. It's often round to oval and may be very plain or decorated with ridges of thin concentric, colorful lines or rays. The Northern Quahog is more colorful than its southern cousin with a beautiful interior decorated with white and deep purple swirls. Prized and part of Native American diets, they used them to painstakingly make the colorful beads for wampum belts served to bind treaties. They grow 3 to 6 inches.
Habitat: Sand or mud in shallow water
Range: Nova Scotia Canada to Florida and Texas
Did you know the Lucines are named for Lucina, an aspect of the Roman Goddess, Juno, who represented light and childbirth? Lucines are common in warm waters on both Atlantic and Pacific Coasts of North America.
The Buttercup Lucine or Lucina, Anodontia alba, is an circular bowl shaped small bivalve with a white outer shell and creamy to butter yellow interior. The exterior has numerous fine concentric lines and a somewhat wide hinge plate. With a fairly sturdy shell, it grows up to 2 inches and is non-edible.
Habitat: Deep to shallow water
Range: North Carolina to Florida and West Indies and U.S. Pacific Coast
The Florida Lucine or Lucina, Pseudomiltha floridana, non-edible, grows to 1 1/2 inches at maturity with weak growth lines but sturdy shell. Both exterior and interior valve colors are white. The shell is fairly inflated, very round with a beak that turns forward and is small, but prominent. They have been called the Face Shell, because they are used for faces of shell dolls.
Habitat: Moderate shallow water
Range: Florida to Texas and U.S. Pacific Coast
Linga pennsylvanica, known as the Pennsylvania Lucine or Lucina is white and grows fully at 2 inches, is non-edible with distinct concentric ridges and a distinct diagonal furrow about the posterior region. The shell is sturdy, heart shaped and inflated with a beak inclined forward. Beach worn specimens are smooth and shiny.
Habitat: Shallow water
Range: North Carolina to Florida and West Indies and Pacific Coast
Ponderous Ark, Noetia ponderosa, is a very thick triangular shell with strong flat ribs and a large beak that turn backwards. They have a dark velvety skin worn to white after beaching or can stain to rust, gray or black. Their robust shells make them and their relatives, the Blood Arks, among the most common beach finds where other bivalve shells are otherwise pulverized in high energy wave zones.
Habitat: A sand dweller in shallow shores
Range: Virginia to Key West and Gulf of Mexico
The Blood Ark, Anadara ovalis, derives its name from its uncommon red blood; most mollusks have clear blood. Like their close relative, the Ponderous Arks, the Blood Arks have very thick shells, only to a slightly lesser degree. At first glance, it's hard to tell them apart, but the Ponderous Ark has more of a triangular shaped shell with an inflated high crease from the beak, whereas the Blood Ark has a more elongated oval shape. You can plainly see the boxier shape of the Ponderous Ark from the comparison photo below. Their hinge lines are slightly different as well, longer and less arched on the Blood Ark. Both species grow to about 2 1/2 inches at maturity.
Habitat: Sandy shallows
Range: Cape Cod, Massachusetts to Florida and east to Texas
The Tranverse Ark, Andara Transversa, is a fairly sturdy, elongated oval and small bivalve, fairly inflated bearing a relatively long straight hinge line. They have squarish ribs and are often colored white with or without dark patches around the edge growing to about 1 1/4 inch max.
Habitat: Gulf and bay sandy bottoms or hard substrates
Range: Massachusetts to Florida and West Indies
The desirable Incongruous Ark, Scapharca brasiliana, formerly Anadara brasiliana, is a sturdy shelled ark well distinguished by obvious beading on its strong radial ribs. They can grow up to 3 inches in a triangular shape with well inflated valves and a strong beak turned back. Color is white with brown furry covering while alive and may discolor after being beached.
Habitat: Gulf and bay sandy bottoms
Range: North Carolina to Brazil
Cut Ribbed Ark
Anadara floridana, otherwise known as, Anadara secticostata, the Cut Ribbed Ark have fairly inflated shells with an elongated, slightly uneven oval shape. Their hinge is long and straight. They can reach up to 4 1/2 inches. Usually colored white, but like other arks, are susceptible to staining rust after beaching. The valve consists of 30-38 radial ribs flattened on top with a groove down the center of each rib and concentric ridges between the ribs.
Habitat: Off shore sands, but closer to shore in Southern Florida
Range: North Carolina, Florida and Gulf of Mexico to Texas and West Indies
Zebra Ark, Turkey Wing Ark or Noah's Ark
Zebra Arks or Turkey Wing Arks, Arca Zebra, have an elongated oval shape with a long straight hinge. The surface of the valve is uneven with rough textured ribs, but their most distinguishing mark is the attractive zigzag alternating brown and white stripes resembling a zebra or, obviously, a turkey wing. This ark shell has also been called “Noah's Ark” because of its shape when the valves are connected. Like many of the arks in general, living examples are covered with a thick and bristly “carpet” or periostracum that wears after beaching. They grow to about 3 1/2 inches.
Habitat: The mollusk attaches itself by its byssus (threadlike filaments) to rocks and other solid objects in shallow water.
Range: North Carolina to the West Indies, and also on Bermuda's shores, as well as in the Mediterranean.
Broad Ribbed Cardita
The Broad-Ribbed Cardita, Carditamera floridana, is also known as the Bird Wing Shell. Average size is 1 inch; largest 1 1/2 inch. The exterior shell is white with purple or chestnut blotches with a white interior. The shell is oval, small, thick with 20 strong raised and beaded radial ribs. Jewelry makers love this little shell which washes ashore commonly on the Florida beaches.
Habitat: Attaches itself to the substrate by means of its byssus (threadlike filaments) in sand or mud 3 to 25 feet deep.
Range: Florida to Texas and Mexico
The Digitate Thorny Oyster, Spondylus tenuis is often mistaken for the Atlantic Thorny Oyster, Spondylus, americanus. Thorny Oysters from the genus Spondylus have many species varying considerably in appearance and range, also known as Spiny Oysters. However, they are not true oysters, yet they do share some habits such as cementing themselves to rocks rather than attach themselves by a byssus, as most bivalves. Also, the two halves of their shells are joined with a ball-and-socket type of hinge rather than with a toothed hinge, as is more common in other bivalves. They have thick lumpy shells most often with thorns, although the Digitate Thorny Oyster has fewer than most. Some varieties are whitish, pink, reddish or orange; growth is up to 3 - 5 inches. Interior is whitish with darker band around the perimeter.
Habitat: Attach to coral reefs or rocky reefs depending on species in shallows or in deeper waters.
Range: North Carolina and Texas southwards to Venezuela and Brazil
Thorny Oyster ?
I wasn't convinced the above seashell is a true Atlantic Thorny Oyster described above, even though one source showed it to be. Most sources show them as more roundish with lots of thorns. Anybody who has information, please feel free to leave it in the comments. It's a really pretty shell, very thick, colorful and pitted. It measures about to 5 inches.
Florida Spiny Jewel Box
Because most jewel box bivalves attach one of their shells to an offshore rock, beachcombers rarely find these beautiful bivalves in their full glory with both valves attached. Look for a thick strongly curved shell with small knobs along 7-9 rows of spines. They're white outside, pinkish inside and usually are 1-2 inches. Presumably, the golden colored sample is staining due to exposure to sun and air.
Habitat: Attached to a rock or shell in warm shallow water
Range: North Carolina to Florida and Gulf of Mexico
Common Jingle Shells
Common Jingle Shells, Anomia simplex, is a bivalve with two different thin, translucent, irregular shaped, pearly valves; one curved, usually yellow, silver, whitish or orange, and the other one is flat and whitish with a hole at the apex. It has a fleshy appendage (byssus) which passes through the hole to anchor itself upon rocks, seaweeds, or old shells. Consequently, usually only the upper valve washes ashore. Average size is up to 1 to 2 inches.
Habitat: Shallow waters, beaches, oyster beds, and mollusk shells.
Range: Nova Scotia Canada to Florida, Texas and West Indies
The Tampa Tellin, Tellina Angulus tampaensis, is a thin opaque white (sometimes tinged pinkish orange) rounded oblong bivalve with a shiny white interior and very thin concentric ridges on the exterior. The valve is fairly symmetrical from its somewhat pointed beak. They only grow to about 1 1/2 inches.
Tellin shells belong to a family which is often considered the aristocracy of bivalves. Of several hundred species, a score are found along our coasts, especially in the warmer waters of the Atlantic and Gulf. They are diverse in size 1/4 to 4 inches, but all are relatively thin and compressed. The hinge is not strong and shells washed up on the beach are often broken. Some Tellins are rose colored and attractive with banded patterns desirable to collectors, but most are white to creamy. There's plenty of photo samples on the internet for viewing more of the varieties.
Habitat: Shallow sand and grassy inland bays and lagoons
Range: Florida to Panama and Texas
Interrupted Tellin or Speckled Tellin
The Interrupted Tellin, Tellina listeri, also known as, Speckled Tellin, grows average size of 1 inch, the largest 2 inch. They are non-edible. Exterior valve is creamy-white with purplish brown rays or speckling. The interior is white with the colors showing through. The shell is moderately thin, long and oval. The valve has strong concentric lines and a crease extending from the beak to the edge
Habitat: Moderately shallow water, but buries itself deeper in the mud and sand than most bivalves
Range: North Carolina to Florida and Brazil
The Coquina Shells, Donax variabilis, are found in all colors and patterns of the rainbow. The colors can be from yellowish-brown, blue, lavender, green, pink. Many are plaid. Their shells are asymmetrical from their pointed beak, slightly elongated and inflated; and grow to only 3/4 inch.
This is a little clam which creates the activity you see at the tide line of the surf. With aid of its foot it darts about and can bury themselves in a twinkling. Apparently, they are sensitive to light and rush to get back into darkness under the sand. The are great in soup and crafters desire them for their beauty.
Habitat: Sandy shallow subtitle zones
Range: Virginia to both coasts of Florida and Texas
I was unable to find information about the two photo samples above, not from the internet, nor from the books I have. They are creamy in color, extremely smooth, absolutely no ribs or spines, and are very thick. If anybody knows something about them, feel free to leave any info you may have in the comments.