Simplify the following text for a Grade 9 native English-speaking person.
Original: The knobbed whelk , Busycon carica , is a species of very large predatory sea snail , or in the USA , a whelk , a marine gastropod mollusk in the family Buccinidae , the busycon whelks .
Simplified: The Knobbed Whelk ( Busycon carica ) is a gastropod mollusc which is protected by a thick , hard shell .