Penion cuvieranus is a species of very large predatory sea snail or true whelk, a marine gastropod mollusc in the family Buccinidae, the true whelks. Snail is a common name for almost all members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in a general sense, it includes sea snails, land snails and freshwater snails. Otherwise snail-like creatures that lack a shell (or have only a very small one) are called slugs. The three species of the Giant African land snail Achatina fulica can grow to be 15 in (38 cm) from snout to tail, and weigh 1 kilogram (2 lb).