The Conchological Society of Great Britain and Ireland

Body (excluding appendages)

Up to 30 mm long. Dorsally brown  [2] with opaque white flecks which concentrate in places into patches of white, two of which may resemble false eyes anterior to rhinophores [1].

Cerata
Numerous. Arranged along sides and across anterior and posterior of body, completely surrounding, and sometimes partially concealing, the dorsum.
Many wart-like papillae on surface, and one on apex [11]. Translucent whitish, shading to hyaline green basally [2], hence J. hyalinus from Latin hyalus = glass green. Lateral cerata have a brown internal digestive gland extending half  way up, or less [11]. Those across the posterior, and those anterior to the rhinophores, have no digestive gland. Many small flecks and streaks of brown, white and yellowish white pigment on surface.

Rhinophores  [5]
Truncated apex. Numerous elongate rib shape warts orietated obliquely along the rhinophore. Brown with much yellowish white freckling, especially on warts. Similarly coloured large wrinkled caruncle between the bases of the rhinophores [8].

Head
Partly covered with cerata. Seen from below; a small oral veil, translucent white freckled yellowish white, extends laterally into oral tentacles [3]. Mouth yellowish white. Small eye at base of each rhinophore.

Foot
Broad until posterior of body, from where the projecting metapodium tapers rapidly [4]. Bilaminate anterior edge smoothly rounded with no propodial lobes or tentacles. Sole transparent whitish, clearly revealing internal anatomy and the white freckles on the dorsal surface of the foot [3].