Small drill shell
| Small drill shell | ||||||||||||
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Barnea parva (Pennant, 1777) |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Barnea parva | ||||||||||||
| ( Pennant , 1777) |
The Small piddock ( Barnea parva ) is a drilling in hard substrate shell -Art from the family of lithophagous molluscs (Pholadidae) in order of Myida is provided.
features
The same-folding, inflated housing is approximately elliptical in outline with a slightly elongated rear end. It is unequal, with the vertebrae in front of the midline. It grows up to four inches long, at a height of; this results in a length-to-width ratio of about 2. However, the housing outline or housing shape is somewhat variable and depends on the substrate in which the specimen drills. The two flaps gape strongly at the front end. In the vertebral area there is an additional, irregularly lanceolate shell plate. The dorsal ( protoplax ). The rear end is rounded, the front end beaked and trimmed. The ligament is small and sits on internal chondrophores. Noticeable is an elongated cone pointing vertically downwards that attaches below the vertebra. The anterior dorsal margin is turned upwards outwards; the edge protrudes slightly beyond the vortex. The mantle bay is very deep and extends to about the level of the vertebrae. The ventral sphincter is very clear.
The skin is whitish and firm. The ornamentation consists of beads parallel to the edge, which intersect with close-fitting, radial ribs. In the back of the case, the ribs are fine and weaker than the beads. In the front part of the housing, the ribs are stronger than the beads parallel to the edge. The points of intersection of the ridges and ribs are drawn out into small thorns. Accordingly, they are more strongly developed on the front housing part than on the rear housing part. The thorns form a serrated edge around the front gaping opening. The inner edge, on the other hand, is smooth. The periostracum is thin and straw yellow.
Similar species
The white burr mussel ( Barnea candida ) is larger and clearly more elongated in outline. The front part of the case is not beaked. The rear edge is much more rounded than that of the small drilling mussel. The shell is much thicker and firmer than that of the thin-shelled white drill.
Geographical distribution, habitat and way of life
The distribution area of the small drill mussel extends from the south-western coast of England and the English Channel coast to the Mediterranean. It occurs from the tidal range to the shallow subtidal (about 10 m).
In the area of the canal, she prefers to drill in softer rocks such as writing chalk, Old Red sandstones and Jura rocks.
Taxonomy
The taxon was established by Thomas Pennant in 1777 . It is generally valued as a valid taxon. It is the type species of the genus or subgenus Anchomasa Gray, 1852, which is now considered a synonym of Barnea . Fritz Nordsieck used Anchomasa as a subgenus of Barnea .
supporting documents
literature
- Fritz Nordsieck : The European sea shells (Bivalvia). From the Arctic Ocean to Cape Verde, the Mediterranean Sea and the Black Sea. Gustav Fischer Verlag, Stuttgart 1969, p. 152.
- Guido Poppe and Yoshihiro Goto: European Seashells Volume 2 (Scaphopoda, Bivalvia, Cephalopoda) . Verlag Christa Hemmen, Wiesbaden 1993 (reprinted unchanged in 2000), ISBN 3925919104 , p. 131.
Individual evidence
- ^ Thomas Pennant: British Zoology. Vol. IV. Crustacea. Mollusca. Testacea. White, London 1777, p. 77 , Plate XL (online at the Biodiversity Heritage Library ).
- ^ MolluscaBase: Barnea parva (Pennant, 1777).
