1. Trivia arctica with mantle half retracted. Dark marks frequent on edge of mantle but never on the shell. Usually less common live on shore than T. monacha, but 100+ seen on a shore on Menai Strait, Wales August 2010.
2. Trivia arctica with mantle half retracted. Dark marks frequent on edge of mantle but never on the shell. Usually less common live on shore than T. monacha, but 100+ seen on a shore on Menai Strait, Wales August 2010.

Trivia arctica with mantle half retracted. Dark marks frequent on edge of mantle but never on the shell. Usually less common live on shore than T. monacha, but 100+ seen on a shore on Menai Strait, Wales August 2010.