Eitehr contact the seller that had them at the sell or the auction house. They should have known they needed transfer papers.I think the best thing you could do is either try to get ahold of the former owner, or call the US Fish and Wildlife Service and ask about a permit, but DO NOT mention you already have them. You might be able to fill out something like this and then they'd be legal to own for you.
Do not all the US fish and Wildlife services. You have to get transfer papers from the person you got them from. If you call USFWS they may send someone out. and you don't want that