Myida (formerly Myoida) is an

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...

of saltwater and freshwater clams,

marine Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military * ...

and

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...

bivalve 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, bival ...

mollusc Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...

s in the subclass

Heterodonta Heteroconchia is a taxonomic infraclass of saltwater clams, marine bivalve molluscs, belonging to the subclass Autobranchia This infraclass includes the edible clams, the cockles and the Venus clams. Description These bivalves are distinguis ...

. The order includes such bivalves as

soft-shell clam Soft-shell clams (American English) or sand gaper (British English/Europe), scientific name ''Mya arenaria'', popularly called "steamers", "softshells", "piss clams", "Ipswich clams", or "Essex clams" are a species of edible saltwater clam, a ...

geoduck The Pacific geoduck ("gooey-duck"; ; ''Panopea generosa'') is a species of very large saltwater clam in the family Hiatellidae. The common name is derived from the Lushootseed ( Nisqually) word . The geoduck is native to the coastal waters of t ...

s and

shipworm The shipworms are marine bivalve molluscs in the family Teredinidae: a group of saltwater clams with long, soft, naked bodies. They are notorious for boring into (and commonly eventually destroying) wood that is immersed in sea water, including ...

Description

They are burrowing molluscs with well-developed

siphon A siphon (from grc, σίφων, síphōn, "pipe, tube", also spelled nonetymologically syphon) is any of a wide variety of devices that involve the flow of liquids through tubes. In a narrower sense, the word refers particularly to a tube in a ...

s. The shell is relatively soft and lacks a

nacre Nacre ( , ), also known as mother of pearl, is an organicinorganic composite material produced by some molluscs as an inner shell layer; it is also the material of which pearls are composed. It is strong, resilient, and iridescent. Nacre is f ...

ous layer. Some species have a single cardinal tooth.

Superfamilies and families

Superfamilies and families within the Myida include: * Superfamily:

Dreissenoidea Dreissenoidea is a superfamily of brackish water and freshwater false mussels, aquatic bivalve molluscs in the order Myida. Families Families within the superfamily Dreisseniodea include: *Dreissenidae The Dreissenidae are a family of smal ...

** Family:

Dreissenidae The Dreissenidae are a family of small freshwater mussels, aquatic bivalve molluscs. They attach themselves to stones or to any other hard surface using a byssus. The shells of these bivalves are shaped somewhat like those of true mussels, and t ...

* Superfamily: Myoidea ** Family:

Corbulidae Corbulidae is a family of very small saltwater clams, marine bivalve molluscs in the order Myida. Genera and species Genera and species in the family Corbulidae include: * '' Anisocorbula'' Iredale, 1930 * '' Apachecorbula'' Olivera, 2014 ** '' ...

** Family:

Myidae Myidae, common name the softshell clams, is a taxonomic family of marine bivalve molluscs in the order Myida. Genera Genera within the family Myidae include: * '' Cryptomya'' ( Conrad, 1848) **'' Cryptomya californica'' ( Conrad, 1837) – Calif ...

** Family: † Pleurodesmatidae ** Family: † Raetomyidae * Superfamily: Pholadoidea ** Family:

Pholadidae Pholadidae, known as piddocks or angelwings, are a family of bivalve molluscs similar to a clam. Background Piddocks are unique in that each side of their shells is divided into 2 or 3 separate sections. Furthermore, one of the piddock's shells ...

** Family:

Teredinidae The shipworms are marine bivalve molluscs in the family Teredinidae: a group of saltwater clams with long, soft, naked bodies. They are notorious for boring into (and commonly eventually destroying) wood that is immersed in sea water, includin ...

** Family:

Xylophagaidae Xylophagaidae is a family of deep-sea woodboring bivalve molluscs, similar to shipworms The shipworms are marine bivalve molluscs in the family Teredinidae: a group of saltwater clams with long, soft, naked bodies. They are notorious for bor ...

* Superfamily: † Pleuromyoidea ** Family: † Ceratomyidae ** Family: † Pleuromyidae ** Family: † Vacunellidae

References

* Powell A W B, ''New Zealand Mollusca'', William Collins Publishers Ltd, Auckland, New Zealand 1979

External links

Animaldiversity

Taxonomicon
Bivalve orders {{bivalve-stub