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.
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.
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.
