Here’s a natural heart for Valentine’s Day. The lovely heart-shaped feature shown in the photograph is an area of the shell called the lunule. The shell in question is a Hard Shell Clam or Quahog – Mercenaria mercenaria (Linnaeus) – that was found at Studland Bay in Dorset, UK – although it is actually an introduced species in the UK.
Each part of a seashell can be described in a precise way that indicates position and function, which enables identification to species level, and allows comparisons to be made between specimens and types.
The lunule is a depressed area in some bivalved mollusc shells, located in front of the beaks or umbones (the bumps that stick out near the hinge), in one or both valves (as in the quahog shown in this post), differentiated from the rest of the shell by a change in growth line pattern or colour.
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