Ryan Photographic - Pectinidae - Scallops
Family Pectinidae
The family Pectinidae contains over 300 species in 60 genera. They are typically called scallops. Unusually, amongst the bivalves, many scallop species can swim by flapping their valves (shells). They do this in response to threats. Threats are detected through an array of eyes, up to 200 in some species. Eyes in scallops are unique, utilizing a concave parabolic mirror instead of a lens and a double retina system. You can read about these eyes here.
Those eyes make approaching bottom dwelling scallops difficult as they swim away, reminding me of those clacking plastic denture toys. Most scallops are good to eat and it is the large adductor muscles that are harvested.
The clams in the genus Pedum (see photos below) bore into massive corals. This may be a mutualistic relationship as the inflowing water current from the clam brings food. In addition, blasts of water from the clam can drive away crown-of-thorns seastars. You can read about these phenomena here.
Pecten novaezelandiae Common scallop
Pecten novaezelandiae Common scallop, Fiordland,New Zealand
Pecten novaezelandiae Common scallop showing eye
Pedum spondyloideum Coral scallop
Pedum spondyloideum, Kadavu, Fiji.
Pedum spondyloideum, Kadavu, Fiji. IMG_9329
Pedum species
 Raja Ampat, West Papua IMG_2744 med res.jpg)
Pedum species Raja Ampat, West Papua IMG_2744