Oyster

This is the left valve from Ostrea edulis, the edible or European flat oyster, pictured washed up on a beach near Kilchoan. It's also called a Colchester oyster, the Essex town being famous for this gastronomic delicacy.

What possesses oysters to live in the muddy waters of the Colne Estuary when they could move up here, into the crystal-clear Sound of Mull, is beyond The Diary's comprehension.

Many thanks to Kilchoan Early Bird for the photo.