Atrina vexillum   (Born,  1778) (Clam)
Organism information awaits expert curation
Class: Bivalvia

Image copyrights: dkimages

Size: Maximum shell length 48 cm, commonly to 30 cm.

Color: Outside of shell dark reddish brown to nearly black, usually dull. Shell material semi translucent, appearing a rich reddish purple when viewed with transmitted light. Interior dark brown to black, iridescent on nacreous area.

Shell reaching a very large size, thick and solid, inflated, variable in shape from triangular to hatchet-shaped or sub-globular with a thin wall. Dorsal margin usually nearly straight, posterior margin broadly oval to somewhat truncate in outline, ventral margin broadly convex posteriorly and concave near the umbones, often strongly lobate in medium-sized and large specimens. Outside of valves with 10 to 17 main radial ribs, often bearing scale-like spines, and with weaker interstitial riblets. Internal nacreous layer moderately strong, undivided, occupying the anterior half or 2/3 of valves. Hind margin of posterior adductor scar slightly protruding beyond the nacreous area (protrusion of adductor scar more developed in mature specimens).

Synonym (s)
Pinna nigra Chemnitz, 1785
Pinna vexillum Born, 1778
Atrina gouldii banksiana Iredale, 1939
Pinna gubernaculu Roding, 1798
Pinna nigra Dillwyn, 1817
Pinna nigrina Lamarck, 1819

Common Name (s)
• Indo Pacific Pen Shell
Economic Importance and Threats
Importance:  Commercial
(The large posterior adductor muscle is highly prized as food, and the black shell carved to make decorative ornaments or plates. Beautiful but very fragile black pearls are sometimes produced by the animal.)

Habitat:  Rocky, Sandy, Coastal
Trophic Level:  Consumer


• Andaman and Nicobar Islands INDIA
• Tamil Nadu, Dhanushkodi INDIA
• Tamil Nadu, Gulf of Mannar (Lat: 78.13) (Long: 8.58) INDIA (Record: 01/1994-12/1995)
• Tamil Nadu, Gulf of Mannar (Lat: 79.5) (Long: 9.33) INDIA (Record: 01/1994-12/1995)

Literature Source(s)
  • Tikadar, BK; Daniel, A and Subbarao, NV (1986) Sea shore animals of Andaman and Nicobar Islands The Director, ZSI, Kolkatta 188 Available at - ZSI, Pune
  • Subba Rao, NV and Dey, A (2000) Catalogue of marine molluscs of Andaman and Nicobar Islands Occasional paper no 187 Records of the Zoological Survey of India ZSI 1-323 Available at - NCL, Pune
  • Allen, GR (2005) Reef fishes of northwestern Madagascar RAP Bulletin of Biological Assessment 31 39-48
  • Hosseinzadeh, H; Daghoghi, B and Rameshi, H (2001) Atlas of the Persian Gulf molluscs Oman sea fisheries research center, Oman 208 Available at - NIO, Goa
  • Poutiers, JM (1998) Bivalves FAO species identification guide for fishery purposes. The living marine resources of the western central Pacific. Volume 1: Seaweeds, corals, bivalves and gastropods FAO, Rome 1 686 pp Available at -
  • Society for the Management of European Biodiversity Data (2009) World Register of Marine Species (WoRMS) Available at -
  • Samuel, VD; Chacko, D and Edward, JKP (2005) Preliminary study on the molluscan diversity of “the lost world’’– Dhanushkodi, east coast of India Proceedings of the National Seminar on Reef Ecosystem Remediation SDMRI Special Research Publication No.9 54-58 Available at -
  • Available at -
  • Hameed, PS and Somasundaram, SSN (1998) A survey of bivalve molluscs in Gulf of Mannar, India Indian Journal of Fisheries Indian journal of Fisheries for the Indian Council of Agricultural Research, Kochi, India 45(2) 177-181 Available at -

Page last updated on:2012-03-07

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