The bivalve seashells, or shells that come in two parts or halves, can be similar in appearance, but not all bivalves are “clams”. I’m not scientifically minded, but I’ve been learning the difference between the shells I collect and photograph.
I’ve gathered some photos of the more common bivalves I see on beaches and in the saltwater rivers around my area of Florida. A general bivalve list includes: clams, oysters, scallops, cockles and mussels.
Clams and Arks
My photos below in this section contain various types of clam shells. Also, there are many types of Venus clams and loads of coquina clams. Shells called “arks” are also clams.
Tagelus clam shell
big clam shell
Ponderous Ark
Transverse Arks (Anadara transversa)
Dosinia clams
Turkey Wing – ark
jackknife clam (with pen shells)
Channeled duckclam
The Spiny Jewel Box is a shell found mostly on the Gulf Coast and possibly the Keys. The Cardita shell is the only one I’ve ever seen and was found on the east coast beaches where I live.
The broad ribbed cardita, measures about an inch in length.
Spiny Jewelbox
Oysters
I rarely collect oyster shells but we see oyster beds while out on our boat. Oyster shells are sharp, and are the scourge of boaters because they can slice up the underside if a bed is accidentally hit while running. While walking the flats in oyster areas I can hear the shells snapping as they feed.
Oyster Shells
Oysters among the mangroves
Oyster bed at low tide
Scallops
Scallop shells can be some of the prettiest shells. Certain types of scallops have one flat side and the other is normal / rounded. The concave part is in the sand or bottom and the flat part is on top and opens like a flap when the scallop is alive. Scallops propel themselves around by opening and closing their shells.
The Kitten Paw and larger Lion’s Paw shells are also scallops. I found these Kitten Paw shells while visiting Sanibel Island on the Gulf coast. I’ve never seen any where I live on the east coast.
2 inches across
Calico Scallops and one Cross-barred venus clam shell
Kitten’s Paw Scallop Shells
Cockles
Cockles are not clams although they look similar. Because they have an oval shape with high top part (umbo), when a whole cockle is viewed from the side it resembles a heart. For that reason, they are known as the heart shell or heart cockle.
Heart cockle
yellow pricklycockles
Yellowish pricklycockle with a piece of a pear whelk turning black
Atlantic Giant Cockle Shell
Once cleaned up, the inside of the giant cockle is mauve pink.
Beautiful coloring on this bivalve
Mussels
Mussel shells are something I rarely collect or photograph because they really are not great looking shells. They are dark colored and shaped like thin fans. The pen shell is distantly related and I have a few pictures here. The pen shell can be nearly a foot in length and is more impressive than a mussel.
While photographing my newly collected shells the other day, I decided to re-photograph my pretty scallop shells. Florida waters can contain a variety of types of scallops, but the shells I find over here on the east coast are mainly the Atlantic Calico Scallop.
Ponce Inlet, Florida’s central east coast
While beachcombing in my area of Florida, the best shells are often found around Ponce Inlet and the jetty area. Because of the rough surf and strong currents many of the shells are broken, worn, or have turned black. When I say “best shells” I mean the most unusual or rarely seen while I search the sand. I sometimes find olive shells here, big angel wings, scallops, and bits of coral. On this day, I found a pretty little pink scallop and a couple that were blackened from being buried in the sediment for a long time.
Pink and Black Scallop Shells
Jetty rocks and barnacles
Rock Jetty at Ponce Inlet in New Smyrna Beach
Barnacle and rock
Ribbed barnacle and jetty rock
Photographing Scallop Shells
Sometimes photos can show a clearer picture of the intricate details of a seashell. The calico scallop, when found before it’s colors fade or turn black or orange, is quite pretty. I have a few of those and you can see the color variety in my photo below. Colors tend to be off-white, cream and yellow with blotches of maroon and pink.
Notice that some of the “ears”, or protrusions at the front of the shell, have worn down or off completely on some shells.
I’ve taken some macro photos to show the ribs on the shells a bit better. Other types of scallops that can be found in Florida waters are the Zig Zag and Round Ribbed, Rough Scallop, Scaly Scallop and famous Lion Paw (very rare). The Bailey-Matthews Museum on Sanibel Island has come good photos Florida’s scallops. See the set under the Family Pectinidae on their site.
The Round Ribbed and Zig Zag scallop have flat tops so as a bivalve each side looks different. You may find the colorful flat piece or the bottom, less colorful part. The Scaly scallop is more elongated and one of it’s “ears” is much longer than the other.
Bay scallops are now rarely found, according to the Living Beaches book (affiliate link to Amazon, new book version). Their ribs are more squared, but when I look at photos I can’t really see much difference between the Bay and Calico as far as shape. Because the Bay Scallop is now rare, I assume my shells are all Calico varieties.
While I write often about the seashells and sea snails I encounter on my travels, I sometimes forget what people really want to know about seashells. On this page I will answer some common seashell questions. I’m not a scientist, so my answers are simple and come from my own observations and research.
How do I identify my seashell?
To identify a seashell you’ve found, first you must know if it’s a gastropod or bivalve. This greatly narrows down options. Does your shell come as one piece or two? Spiral shells are gastropods (one-piece) and clams and scallops, as an example, are bivalves. Bivalves were created as two halves even though we most often find only one of the halves.
A shell that can be tricky is the slipper snail shell. For a long time I assumed it was a bivalve, but it is a gastropod because it is made in one piece.
The Slipper Snail is a Gastropod
Top of a slippersnail shell (Gastropod)
slipper snail shell, bottom
The shells shown below are identified as gastropods or bivalves. This blog has a page of commonly found shells that are seen in Florida, where I live. I can’t identify your shell for you if you live in another part of the world! There are millions of seashells and even the same species can have great variety.
Murex – gastropod
Bivalves
Combination
Next, search for shells that are found locally wherever you found your shell. Even if it’s an uncommon shell, chances are that someone before you has collected the same type of shell. Search blogs, forums, and books that mention shells found in that area of the world. The Bailey-Matthews National Shell Museum is a good place to search.
Also, know seashell lingo. Along with the size, a shell is often described by mentioning the aperture (opening), body, whorls, lip, tooth, columella, hinge, etc. Color is important too, but sometimes the same types of shells can vary widely in color. Here is an excellent page, and site, to direct Florida shell collectors to identifying their shells.
What lives inside a shell?
Snails live inside shells. They create the shell as they grow. There are land snails and sea snails. Mollusks are snails of the sea and they make hard coverings (the shell) to conceal their soft bodies. However, once the mollusk dies and leaves an empty shell behind, other creatures can move in. Namely, hermit crabs. Where I live, I find lots of hermit crabs living inside shells.
Tulip shell with snail
Lightning Whelk snail
hermit crab inside whelk shell
Other living things can attach themselves to shells also and they don’t really care who is living inside the shell. See the barnacles on the shells below.
Horse Conch
Tulip
Are starfish (sea stars) and sand dollars considered to be seashells?
No, sea stars and sand dollars are echinoderms. There is no snail living inside them and they are completely different from snails that build shells. People do tend to call them “shells” mainly because they are found on the beach.
I rarely see sand dollars or sea stars, but I was lucky enough to come across this very tiny sea star on one of our boating trips.
sand dollar
sea star
How are seashells made? Where do seashells come from?
The snail creates the shell from what it eats and minerals it takes in during it’s life. The snail secretes a substance to build the shell around it and expand upon it’s home as it grows. The shell color also comes from what it eats.
Baby snails hatch from casings left by the parent snail. They begin very small and usually thousands of babies inhabit the casings because it’s so tough to survive in their habitat. This is a good place to mention that you should never collect a living seashell, or shells that have anything living inside or attached to the outside of the shell.
Egg Cases From Two Types of Sea Snail
On the left, the shark’s eye snail made this round, rubber ring that holds babies waiting to hatch. The egg case on the right belongs to some sort of whelk, but I’m not sure which. I’m holding a little Cerith shell next to it for size comparison.
Shark’s eye egg casing
Egg case holding baby sea snails
My Interest in Seashells
I don’t know what it would be like to live far from an ocean. I grew up in Massachusetts, but even then I visited Wells Beach in Maine in summer, or went to Hampton Beach in New Hampshire with friends.
I wasn’t paying much attention to seashells back then. Being young, I was focused on more important things. Then, I lived in Florida for most of my adult life. The east coast beaches were only about thirty minutes away and we took the kids to the beach often. Now, the beach is even closer to my house. The point is that an ocean beach has always been within driving distance in my life.
Now that I am older, I prefer to scour the sand for interesting wildlife, plants, and shells that have washed up. At this point, it’s my favorite part of Florida. The crowds of people that have infiltrated this state have made enjoying natural Florida nearly impossible. So, we get on our boat and go off into the rarely visited waterways that snake through the Mosquito Lagoon estuary. My son fishes, and I walk the low-tide sand bars and mangrove island beaches.
Whenever I find something unusual I get photos and add them to my blog. I write about what I see, and the research I do is to inform myself and others. I hope that this will enlighten readers to the amazing world of sea snails and the shells they create. Knowing is appreciating.
I’m very lucky to be able to get out and view this nature for myself. All photography on this page is my own, as is most of the photography on this site. I use some of my photos for the design work I do and sell postcards, paper, puzzles and other products in my online store Seashells by Millhill.
I don’t have a problem with people collecting empty shells, but I am against buying shells from shops. It’s a money-making venture, which causes the death of living sea snails.
Do you have a seashell question? Leave it in the comments and I’ll try to answer it.
