sentence1: Propilidium pelseneeri is a species of sea snail , a true limpet , a marine gastropod mollusk in the family Lepetidae , one of the families of true limpets .
sentence2: Propilidium pelseneeri is a species of sea snail , a true limpet , an appropriate gastropod mollusk in the Lepetidae family , one of the families of marine limpets .