Description: This rare Arminacean is very similar in appearance to Janolus hyalinus, but may be immediately distinguished from that species by the absence of the caruncle between the rhinophores. The body and cerata are pale fawn with brown mottling, and there are spots of white pigment on the cerata and body. The cerata are covered in small bumps and the rhinophores are tuberculate or wrinkled. Measures up to 13mm in length.

Habitat: Reported from amongst sponges, bryozoans and hydroids, mostly from sheltered locations. The spawn is a wavy spiral.

Distribution: This species is apparently very rare, and has only been seen once in the British Isles since 1937, in Loch Torridon, W. Scotland. It was originally described from Malahide, near Dublin. Recorded from outside the British Isles only from the Atlantic coast of France.

Key Identification Features:

• Pointed cerata with rough surfaces.
• Cerata extend across front of body.

Distribution Map from NBN: Proctonotus mucroniferus at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Proctonotus mucroniferus at iNaturalist World Species Observations database.

WoRMS: Proctonotus mucroniferus at World Register of Marine Species. Accepted name: Proctonotus mucroniferus (Alder & Hancock, 1844). AphiaID: 140858.

Classification: Biota; Animalia; Mollusca; Gastropoda; Heterobranchia; Euthyneura; Ringipleura; Nudipleura; Nudibranchia; Cladobranchia; Proctonotoidea; Proctonotidae; Proctonotus