Spiny pink scallop (Chlamys hastata) shells/valves have sharp spines on their ridges, which you can see in the lower left corner of the photo.
The spiny pink scallop is also known as a swimming scallop. If this animal is disturbed it may start opening and closing its shells which offer a form of propulsion, allowing the scallop to lift up into the water and fall downwards a short distance away, hopefully avoiding predation. The spiny pink scallop can be orange, reddish or pink in colour, and has sharp spines on the radiating shell ridges, and the edges of the shells are fluted. This scallop can be difficult to identify on a dive as often these spines and ridges are hidden beneath sponges living on the shells, but some major radiating ridges may still be seen as small mounds through the encrusting sponge. The spiny pink scallop can grow to 3.7 inches (9.3 cm) across, with a range from southern Alaska to southern California.
Reference:
Jensen, Gregory with Gotshall, Daniel and Flores-Miller, Rebecca. Beneath Pacific Tides: Subtidal Invertebrates of the West Coast. Bremerton: MolaMarine, 2018.
