Description: This bivalve looks slightly different depending on age. In young animals the shell is brittle with a dorsal plate composed of 2 triangular plates. There is a prominent pedal gape. The shell is rounded posteriorly.

In older animals the shell resembles that of the younger animals except that an additional section (callum) is added that closes the pedal gape and grows up over the umbones. In addition the posterior rounding becomes truncated and the 'siphonoplax' grows from this area. It is made up of chiton formed into tube-like structures.

Overall the shell is white with a straw coloured periostracum and siphonoplax. There is a structure of concentric ridges on the outer surface of the shell divided by a deep median groove. The callum (see above) lacks this structuring.

Habitat: Bores into mud, clay, peat and soft sandstone from low water onwards.

Distribution: A few scattered records from around Britain and Ireland. Not common.

Similar Species: Unlikely to be confused with any other species.

Key Identification Features:

• Distinctive shape to shell which is divided by deep median groove.
• Slightly different forms in young and old specimens which should be noted.
• Distinctive siphonoplax which, if present, should help distinguish this species.

Distribution Map from NBN: Pholadidea loscombiana at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Pholadidea loscombiana at iNaturalist World Species Observations database.

GBIF data for Pholadidea loscombiana

WoRMS: Pholadidea loscombiana at World Register of Marine Species. Accepted name: Pholadidea loscombiana W. Turton, 1819. AphiaID: 140769.

Classification: Biota; Animalia; Mollusca; Bivalvia; Autobranchia; Heteroconchia; Euheterodonta; Imparidentia; Myida; Pholadoidea; Pholadidae; Martesiinae; Pholadidea