You can store the Ankheg shells in any container. How it works with the smithy in Beregost:
He buys them for 500 gp - but he takes all the shells you have in your inventory. To get 500 gp
per shell, just ground all but one, sell that one, pick up another and repeat. He will continue to buy them until he makes the armor for you. He is the only one who will give you a lot of money for them, so after that, IMO, it's not worth it to lug around ankheg shells. (They're heavy.) Go Winter Wolf hunting instead - the shopkeeper in Nashkel will always buy the pelts from you.
