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 nacreous 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).
- Atrina fragilis (Pennant, 1777) — fan mussel
- Atrina nigra (Dillwyn, 1817)
- Atrina seminuda (Lamarck, 1819) — half-naked pen shell
- Atrina serrata (Sowerby, 1825) — saw-toothed pen shell
- Atrina rigida (Lightfoot, 1786) — stiff pen shell
- Atrina vexillum (Born, 1778) — flag pen shell
- Atrina zelandica (Gray in Yate, 1835) — the horse mussel
- Packard, Earl; Jones, David L. (Sept. 1965). "Cretaceous Pelecypods of the Genus Pinna from the West Coast of North America". Journal of Paleontology 39 (1): 910–915.
- "Glossary". Man and Mollusc. Archived from the original on 18 January 2008. http://www.manandmollusc.net/glossary.html. Retrieved 2008-01-30.
- Mitchell, Patricia B.. "American Stiff Pen Shell: Strength and Rigidity". Archived from the original on 20 December 2007. http://www.mitchellspublications.com/guides/shells/articles/0046/. Retrieved 2008-01-31.