Eoacmaea calamus is a species of sea snail , a true limpet , a marine gastropod mollusc in the Eoacmaeidae family , one of the families of true limpets . Eoacmaea calamus is a species of sea snail , a true limpet , a marine gastropod mollusk in the family Eoacmaeidae , one of the families of true limpets . Eoacmaea calamus is a species of sea snail , a real limpet , a true gastropod mollusk in the Eoacmaeidae family , one of the families of naval limpets .