A shadow over the cup of an upturned cockle shell. Shadows also set off the fluting along the margin. This is the shell of the heart cockle, Clinocardium nuttallii.
I like the shifting influence of sunlight and shadows on the ribs radiating over the cockle’s curved external surface. Next time you come across a complete heart cockle shell, see if you count 35 ribs.
If this post hasn’t satisfied your cockle curiosity I’ve just opened a Bivalves page where you can see more images of heart cockles (and even lean why they’re called heart cockles) and get my take on a few other common bivalves.
theoutershores 
I just rushed off to count the ribs n a couple of cockle shells in my possession (yes, I do have random shells that I like in various places) and yes! Thirty five it is! It had never occurred to me to wonder, but I’m pleased to add to my limited knowledge.
I looked at your photos and at first I just saw shells. I read your descriptions and I looked again and saw nature in all its beauty! Thanks 🙂
A unique response to the challenge! Love how each week you help us to learn something about your subjects along with their beauty!
Sweet! A heart cockle for Valentine’s day! 😀
Love your photos, and your comments!