H. arctica. Fused siphons; inhalent taking in water, exhalent closed so siphons swollen and periostracum stretched thin. Two worn ridges, with some spines, run radially from beak to posterior. Wedge-form shell. Byssus near anterior. Menai, March 2011.

Submitted by Ian Smith on Fri, 18/11/2011 20:18
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I.F. Smith
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