Both palaeonemertean and pilidiophoran larvae can be uniformly ciliated and blind. Use these characters to differentiate species:
Thick epidermis, posterior cirrus present. Stiff lateral cirri present or absent.
Apical tuft and posterior cirrus present. Developing juvenile inside is inconspicuous with head pointed toward larval posterior.
Large (500 µm in length), opaque with small apical tuft and posterior cirrus. Color slightly orange-red.
Small, thin larva with posterior cirrus and longitudinal, mid-ventral groove anteriorly.