Technically, yes but technically speaking Nassarius are also classified as Whelks.
I believe this site sells both types under the name Nassarius. The mud snails I refer to are actually Ilyanassa obsoleta. Ilyanassa sp. will reproduce easily in a home aquarium. Nassarius vibex is much more difficult.
The easiest way to tell them apart is Ilyanassa will eat algae, Nassarius cannot eat algae and will starve without a steady supply of carrion.