Bivalvia, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. Bivalves as a group have no head and they lack some usual molluscan organs like the radula and the odontophore. They include the clams, oysters, cockles, mussels, scallops, and numerous other families that live in saltwater, as well as a number of families that live in freshwater. The majority are filter feeders. The gills have evolved into ctenidia, specialised organs for feeding and breathing. Most bivalves bury themselves in sediment where they are relatively safe from predation. Others lie on the sea floor or attach themselves to rocks or other hard surfaces. Some bivalves, such as the scallops and file shells, can swim. The shipworms bore into wood, clay, or stone and live inside these substances.
Unionida is a monophyletic order of freshwater mussels, aquatic bivalve molluscs. The order includes most of the larger freshwater mussels, including the freshwater pearl mussels. The most common families are the Unionidae and the Margaritiferidae. All have in common a larval stage that is temporarily parasitic on fish, nacreous shells, high in organic matter, that may crack upon drying out, and siphons too short to permit the animal to live deeply buried in sediment.
The Ochlockonee moccasinshell is a species of freshwater mussel, an aquatic bivalve mollusk in the family Unionidae, the river mussels.
Freshwater bivalves are one kind of freshwater mollusc, along with freshwater snails. They are bivalves which live in freshwater, as opposed to saltwater, the main habitat type for bivalves.
Coelotrochus chathamensis is a species of small sea snail, a marine gastropod mollusc in the family Trochidae, the top snails or top shells.
A bivalve shell is part of the body, the exoskeleton or shell, of a bivalve mollusk. In life, the shell of this class of mollusks is composed of two hinged parts or valves. Bivalves are very common in essentially all aquatic locales, including saltwater, brackish water, and freshwater. The shells of bivalves commonly wash up on beaches and along the edges of lakes, rivers, and streams. Bivalves by definition possess two shells or valves, a "right valve" and a "left valve", that are joined by a ligament. The two valves usually articulate with one another using structures known as "teeth" which are situated along the hinge line. In many bivalve shells, the two valves are symmetrical along the hinge line—when truly symmetrical, such an animal is said to be equivalved; if the valves vary from each other in size or shape, inequivalved. If symmetrical front-to-back, the valves are said to be equilateral, and are otherwise considered inequilateral.
Lampsilis fasciola, the wavy-rayed lampmussel, is a species of freshwater mussel, an aquatic bivalve mollusk in the family Unionidae, the river mussels.
Propebela rathbuni is a species of sea snail, a marine gastropod mollusk in the family Mangeliidae.
Hindsiclava alesidota, common name the lean turris, is a species of sea snail, a marine gastropod mollusc in the family Pseudomelatomidae, the turrids.
Sharpirhynchia sharpi is a species of extinct, small-sized lampshell, named after Samuel Sharp (1814–1882), an early fossil collector, who discovered the limited time span of some fossils, now known as index fossils. S. sharpi is a marine rhynchonellate brachiopod in the family Rhynchonellidae. It is roughly ½ inch (1.25 cm) measured along the axis, with a slender beak, the brachial valve more convex than the pedunculate valve, and it has 21–31 ribs fanning out from the hinge.
Rhynchonelloidella alemanica is a species of extinct, small-sized brachiopod, a marine rhynchonellate lampshell in the family Rhynchonellidae. It is roughly 9/16 inch (1.4 cm), and has about 15 ribs fanning out from the hinge.
Laternula elliptica is a species of saltwater clam, a marine bivalve mollusc in the family Laternulidae, the lantern shells. It is the largest bivalve found under the surface of the seabed in the Southern Ocean.
Hinge teeth are part of the anatomical structure of the inner surface of a bivalve shell, i.e. the shell of a bivalve mollusk. Bivalves by definition have two valves, which are joined together by a strong and flexible ligament situated on the hinge line at the dorsal edge of the shell. In life, the shell needs to be able to open slightly to allow the foot and siphons to protrude, and then close again, without the valves moving out of alignment with one another. To make this possible, in most cases the two valves are articulated using an arrangement of structures known as hinge teeth. Like the ligament, the hinge teeth are also situated along the hinge line of the shell.
Calliostoma leanum, common name the pretty mouth, is a species of sea snail, a marine gastropod mollusk in the family Calliostomatidae.
Gigantidas tangaroa is a species of deep-sea mussel, a marine bivalve mollusk in the family Mytilidae, the mussels.
Fusconaia burkei is a species of freshwater mussel, an aquatic bivalve mollusk in the family Unionidae, the river mussels.
Hindsiclava calligonoides is an extinct species of sea snail, a marine gastropod mollusc in the family Pseudomelatomidae, the turrids and allies.
Hindsiclava paraconsors is an extinct species of sea snail, a marine gastropod mollusc in the family Pseudomelatomidae, the turrids and allies.
Lioglyphostoma rusum is an extinct species of sea snail, a marine gastropod mollusk in the family Pseudomelatomidae, the turrids and allies.
Megasurcula stearnsiana is a species of sea snail, a marine gastropod mollusk in the family Pseudomelatomidae, the turrids and allies.
