Species Account

Crenella decussata (Montagu, 1808)

Mytiloidea : Mytilidae

Tebble name: Crenella decussata (Montagu)
Smith & Heppell name: Crenella decussata (Montagu, 1808)

To size: Very small, to 4mm. Shell Structure: Thin, brittle. Equivalve: Equivalve. Equilateral: Very slightly inequilateral, beaks just in front of midline and pointing forward. Tumidity: Tumid. Outline: Outline oval, slightly higher than long, ligament (posterior dorsal) margin distinct, short, straight and sloping more steeply than anterior dorsal margin. Contour: Prodissoconch I, about 240μm in diameter, irregularly dimpled; prodissoconch II subcircular, about 800mm in diameter and sculpured with comarginal ridges crossed by discontinuous radial raised threads.

Sculpture: Sculpture of radial riblets these weakly beaded at intersections with underlying and weaker concentric ridges, riblet number increasing with size of shell, new riblets added between others or by divarication resulting in a total of about 50 in the largest individuals. Margin: Inner margin evenly crenulated. Ligament: Ligament behind the beaks, internal on a shallow resilifer about half the length of the posterior-dorsal margin. Hinge: Hinge plate narrow, beneath beaks lies a swollen process with a few irregular crenulations, ligament margin with up to 15 dysodont teeth. Pallial Musculature: Adductor scars of approximately equal size. Periostracum: Very thin, brownish/ greenish. Colour: Transparent white.

Distribution & Ecology

Widely distributed at shelf depths across the northern areas reaching southwest Wales in the west and Dogger Bank in the North Sea.

Depth Range
Continental Shelf (to 200m)

Additional Information & Related Species

Juvenile Description

Larval shell very large, c. 800mm, sculpture of co-marginal ridges and weak radial lines.

Key Features & Similar Species

The only oval mytilid with divaricating decussate sculpture. Crenella pellucida has no radial riblets.

Related Species


Listed are literature citing Crenella decussata (Montagu, 1808). Reference containing the species Type Description is highlighted.

Montagu G 1808. Testacea Britannica - Supplement Exeter. 183pp + pls 17-30.


  • Conchological Society of Great Britain & Ireland
    Provides resources for understanding, identifying, recording, and conserving molluscs
    Check List of European Marine Mollusca
  • MarLIN
    The Marine Life Information Network for Britain and Ireland (MarLIN) provides information for marine environmental management, protection and education. It is a centre of excellence in spatially based and time-series marine biological information and supports good stewardship in the marine environment.
  • NBN Gateway
    National Biodiversity Network's Gateway. Use it to explore UK biodiversity data, as contributed by participating data providers.
  • BivAToL
  • MarBEF
  • Malacological Society
  • Unitas Malacologica
  • Census of Marine Life
  • MarBEF
    MarBEF, a network of excellence funded by the European Union and consisting of 94 European marine institutes, is a platform to integrate and disseminate knowledge and expertise on marine biodiversity, with links to researchers, industry, stakeholders and the general public.

Record last modified: 22/03/2016