What is "volvarina"

Volvarina is a genus of small to very small sea snails, marine gastropod molluscs in the family Marginellidae, the margin shells.

The difference between the genera Volvarina and Prunum is not clearly delineated and is based on morphological differences in the shells. Larger species with a strong callus are classified under Prunum, while the slender species with a thin callus are classified under Volvarina. Many species with characteristics that fall between the two extremes are ambiguous. Until at least 2010 there was no phylogenetic analysis to substantiate this classification.