Knobbed whelk (Busycon carica) Busycon carica is a member of the family Melongenidae and one of roughly fourteen known species of the subfamily Bucyconinae. Members of the genus Busycon are the largest marine gastropods along the eastern coast of the United States. Juvenile whelks have small beads on their shells, while adult whelk shells are thick with spines on the shoulder. Knobbed whelk shells are right-handed and have a long siphonal canal. The outer shell is greyish white to tan and may have some dark brown streaks. The brown streaks are more prominent in juvenile shells. The inner shell ranges in colours from pale yellow to orange and even dark red.