Nudibranch

''Hypselodoris bullockii'' is a species of colorful sea slug or dorid nudibranch, a marine gastropod mollusk in the family Chromodorididae.

''Hypselodoris bullockii'' is quite variable in color. ''Hypselodoris apolegma'', which looks similar to this species , and was assumed to be possibly a different color form of ''H. bullockii''. However, recent phylogenetic data confirm the distinction of the two species, and suggest a sister species relationship between them.