What is the biggest bivalve mollusk, cephalopod mollusk, and crustacean known to man?

The biggest bivalve mollusk is the clam Tridacna, native to the Indo-Pacific, which reaches a weight of 500 pounds. The giant squid, nearly sixty feet long, is the biggest cephalopod. The Alaskan king crab is the largest of the crustaceans, weighing up to 15 pounds, and measuring four to five feet across shell and claws.