Acrembolic

In contrast to Archidoris, N. claurina has a swollen prostate, an acrembolic penis, a strange anastomosis of the vagina and the duct connecting the allosperm receptacles, and, most significantly, minute caryophyllid tubercles.

The acrembolic type has appeared independently several times in gastropods, including some heterobranchs, while the pleurembolic proboscis may have appeared only once.

In the Pyramidellidae, attachment of the gastropod to its host is by way of a sucker situated at the tip of the long, acrembolic proboscis while the jaw, modified to form a buccal stylet, serves to pierce the integument of the host; there is no radula.