Proctonotus mucroniferus
1: cerata continue round anterior of head.
2: no caruncle between rhinophores.
3: many wart-like papillae on surface of cerata.
Small anterior veil extends into oral tentacles.
Adapted from line drawing in Alder & Hancock (1844 – 1854).

There is no character, other than absence of caruncle and a slight variation in rhinophoral lamellae, to distinguish the extremely rarely found P. mucroniferus from J. hyalinus (Alder & Hancock 1844 – 1854). Molecular sequencing is desirable to test the possibility of it being J. hyalinus with caruncle lost by accident or autotomy.