A seashell or sea shell, also known simply as a shell, is a hard, protective outer layer usually created by an animal or organism that lives in the sea. The shell is part of the body of the animal. Empty seashells are often found washed up on beaches by beachcombers. The shells are empty because the animal has died and the soft parts have decomposed or been eaten by another animal.
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. As a group, bivalves have no head and they lack some usual molluscan organs, like the radula and the odontophore. The class includes 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. Shipworms bore into wood, clay, or stone and live inside these substances.
Gryphaea, one of the genera known as devil's toenails, is a genus of extinct oysters, marine bivalve mollusks in the family Gryphaeidae.
Muricidae is a large and varied taxonomic family of small to large predatory sea snails, marine gastropod mollusks, commonly known as murex snails or rock snails. With over 1,700 living species, the Muricidae represent almost 10% of the Neogastropoda. Additionally, 1,200 fossil species have been recognized. Numerous subfamilies are recognized, although experts disagree about the subfamily divisions and the definitions of the genera. Many muricids have unusual shells which are considered attractive by shell collectors and by interior designers.
Sinistrofulgur perversum, the lightning whelk, is a species of very large predatory sea snail or whelk, a marine gastropod mollusc in the family Busyconidae, the busycon whelks. This species has a left-handed or sinistral shell. It eats mostly bivalves.
The Gryphaeidae, common name the foam oysters or honeycomb oysters, are a family of marine bivalve mollusks. This family of bivalves is very well represented in the fossil record, however the number of living species is very few.
Aequipecten is a genus of scallops, marine bivalve mollusks in the family Pectinidae.
Marine invertebrates are the invertebrates that live in marine habitats. Invertebrate is a blanket term that includes all animals apart from the vertebrate members of the chordate phylum. Invertebrates lack a vertebral column, and some have evolved a shell or a hard exoskeleton. As on land and in the air, marine invertebrates have a large variety of body plans, and have been categorised into over 30 phyla. They make up most of the macroscopic life in the oceans.
Atrina is a cosmopolitan genus of bivalve molluscs belonging to the family Pinnidae.
Exogyra is an extinct genus of fossil marine oysters in the family Gryphaeidae, the foam oysters or honeycomb oysters. These bivalves were cemented by the more cupped left valve. The right valve is flatter, and the beak is curved to one side. Exogyra lived on solid substrates in warm seas during the Jurassic and Cretaceous periods.
Isognomon is a genus of marine bivalve mollusks which is related to the pearl oysters.
Pycnodonte is a genus of extinct oysters, fossil marine bivalve mollusks in the family Gryphaeidae, the foam oysters or honeycomb oysters. Shells of species in this genus are found around the world in fossil shell beds from the Valanginian to the Early Pleistocene. They are a commonly found fossil in Cretaceous shellbeds of the Navesink Formation in New Jersey.
Juliidae, common name the bivalved gastropods, is a family of minute sea snails, marine gastropod mollusks or micromollusks in the superfamily Oxynooidea, an opisthobranch group.
Lutraria is a genus of medium-sized marine bivalve mollusks or clams, commonly known as otter shells.
Gigantostrea is an extinct genus of marine bivalve mollusks belonging to the family Gryphaeidae.
Chama gryphoides is a species of cemented saltwater clam, a marine bivalve mollusc in the family Chamidae, the jewel boxes.
Neopycnodonte cochlear is a species of marine bivalve molluscs belonging to the family Gryphaeidae.
Pseudochama is a species of bivalve mollusc in the family Chamidae.
Cremnoceramus is an extinct genus of fossil marine pteriomorphian bivalves that superficially resembled the related winged pearly oysters of the extant genus Pteria. They lived from the Turonian to the Maastrichtian of the Late Cretaceous.
Rastellum is an extinct genus of molluscs, which lived from the Middle Jurassic to the Late Cretaceous. This species is also known as Arctostrea carinata.
