Branchellion parkeri sp. nov. lacks tubercles, has 31 pairs of fully developed gills (although a minute reduced lobe represents a gill on xiii a₂), and is unique in the possession of only 10 pairs of pulsatile vesicles. The genital pores are immediately adjacent on either side of the annulus, xi/xii. This leech is known from species of Raia and Mustelus in New Zealand waters. This species is recognized as probably the same as B. rajae Parker, 1891, but Parker's species is still a nomen nudum, and accordingly a new name is given.