Atrina
Encyclopedia
Atrina is a cosmopolitan genus
of bivalve molluscs characterized by elongated, wedge-shaped shells, distinguished from the genus Pinna
by the lack of any grooves in the nacre
ous lining of the shell, and by the central positioning of the adductor scar.
As with other pen shells (Pinnidae
) they commonly stand point-first in the sea bottom in which they live, anchored by net of byssus
threads. Atrina is considered to represent the more primitive form within the Pinnidae; however, both genera are ancient and represented within the fossil record.
A typical species is A. fragilis
, found in British waters. A. rigida
(Lightfoot
, 1786) is found on the southeast coast of North America and in the West Indies. The type species
is A. nigra (Dillwyn
, 1817, originally P. nigra).
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of bivalve molluscs characterized by elongated, wedge-shaped shells, distinguished from the genus Pinna
Pinna (genus)
Pinna is a genus of pen shells. It is a cosmopolitan genus of bivalve molluscs characterized by elongated, wedge-shaped shells which most commonly stand point-first in the sea bottom in which they live, anchored by a net of byssus threads....
by the lack of any grooves in the nacre
Nacre
Nacre , also known as mother of pearl, is an organic-inorganic composite material produced by some mollusks as an inner shell layer; it is also what makes up pearls. It is very strong, resilient, and iridescent....
ous lining of the shell, and by the central positioning of the adductor scar.
As with other pen shells (Pinnidae
Pinnidae
Pinnidae is a family of large saltwater clams sometimes known as pen shells. They are marine bivalve molluscs in the order Pterioida.The shells are fragile and have a long and triangular shape, and in life they are anchored in sediment using a byssus...
) they commonly stand point-first in the sea bottom in which they live, anchored by net of byssus
Byssus
Byssus means both a silky filament by which certain molluscs attach themselves to hard surfaces, and a rare fabric, also called sea silk and its fibre source.-Word:...
threads. Atrina is considered to represent the more primitive form within the Pinnidae; however, both genera are ancient and represented within the fossil record.
A typical species is A. fragilis
Atrina fragilis
The fan mussel, Atrina fragilis, is a large saltwater clam or marine bivalve mollusc in the family Pinnidae, the pen shells.The fan mussel is one of the largest European bivalve molluscs. It is one of the rarest species of marine mollusc in the United Kingdom .The shell of the fan mussel tapers to...
, found in British waters. A. rigida
Atrina rigida
Atrina rigida, commonly known as the rigid pen shell, is a bivalve mollusc found from the North Carolina coast through the West Indies and to Brazil...
(Lightfoot
John Lightfoot FRS
The Reverend John Lightfoot was an English conchologist and botanist.He was born in Newent, Gloucestershire and educated at Pembroke College, Oxford. He gained a BA in 1756 and an MA in 1766....
, 1786) is found on the southeast coast of North America and in the West Indies. The type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
is A. nigra (Dillwyn
Lewis Weston Dillwyn
Lewis Weston Dillwyn, FRS was a British porcelain manufacturer, naturalist and Member of Parliament.He was born in Walthamstow, Essex, the eldest son of William Dillwyn and Sarah Dillwyn...
, 1817, originally P. nigra).
Species
- Atrina fragilisAtrina fragilisThe fan mussel, Atrina fragilis, is a large saltwater clam or marine bivalve mollusc in the family Pinnidae, the pen shells.The fan mussel is one of the largest European bivalve molluscs. It is one of the rarest species of marine mollusc in the United Kingdom .The shell of the fan mussel tapers to...
(Pennant, 1777) — fan mussel - Atrina nigra (Dillwyn, 1817)
- Atrina seminudaAtrina seminudaAtrina seminuda, or the half-naked pen shell, is a species of bivalve mollusc in the family Pinnidae. It can be found along the Atlantic coast of North America, ranging from North Carolina to Texas and south to Argentina....
(Lamarck, 1819) — half-naked pen shell - Atrina serrataAtrina serrataAtrina serrata, or the saw-toothed pen shell, is a species of bivalve mollusc in the family Pinnidae. It can be found along the Atlantic coast of North America, ranging from North Carolina to Texas and the West Indies....
(Sowerby, 1825) — saw-toothed pen shell - Atrina rigidaAtrina rigidaAtrina rigida, commonly known as the rigid pen shell, is a bivalve mollusc found from the North Carolina coast through the West Indies and to Brazil...
(Lightfoot, 1786) — stiff pen shell - Atrina vexillum (--------, ----) — flag pen shell
External links
- idscaro Images