Peltodoris atromaculata is a species of sea slug, a dorid nudibranch, a marine gastropod mollusk in the family Discodorididae. Slug is a common name that is normally applied to any gastropod mollusk that lacks a shell, has a very reduced shell, or has a small internal shell. This is in contrast to the common name snail, which is applied to gastropods that have coiled shells that are big enough to retract into.