I checked Wiki and Snopes with no luck. I made an inquiry on Snopes, so maybe they'll come up with something.
Yahoo Answers came up with mixed results. Possibly the ones sold as "Ocean" scallops, the large ones with no little gristly part on the side are indeed, cut from the wings of skates, not stingrays. Bay scallops are the real deal.
Wiki notes that diver-harvested scallops are superior to dredged ones because there is less grit and they get to market more quickly.
