Form: Normally consists of groups of flask-shaped lobes, with terminal oscules, resembling a cluster of Scypha sp., but with a common basal crust.

Colour: White, beige.

Smell: None. Slime : None.

Consistency: Firm.

Surface: Even, non-hispid.

Apertures:

• Oscules at tips of lobes, with fringe of short, even spicules.

Contraction:

• None.

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Synonyms: In Burton (1963) this is one of a number of 'Named Forms' grouped under Leuconia barbata, the name he considered valid for the whole complex.

Internal characters

Skeleton: The ectosome has a tangential layer of triradiates and the facial rays of large quadriradiates, with groups of microxea and quadriradiates. The endosomal skeleton consists of small quadriradiates. The skeleton of the chamber layer consists of scattered triradiates and small quadriradiates.

Spicules: Spicules are calcareous. Ectosomal triradiates (a) have rays 200-300 x 15-20 μm. Triradiates of chamber layer (b) have rays 100-1000 x 10-70 μm. Large ectosomal quadriradiates (c) are ca. 650 x 80 μm (ectosome); sagittal quadriradiates of two types, (d) 30-40 μm (paired rays), 60 μm (basal and apical) x 8 μm (chamber layer); and (e) 250 x 6 μm (associated with microxea in ectosome). Endosomal quadriradiates (f) with rays 200-300 μm. Microxea (g) are ca. 60-80 x 5 μm.

Identity: Can be confused with Leuconia gossei (Burton, 1963, p.505) and Leucosolenia nivea (q.v.). The presence of sagittal quadriradiates in the endosomal layer, with large quadriradiates in the ectosome, is diagnostic.

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

iNaturalist: Leuconia johnstonii at iNaturalist World Species Observations database.

WoRMS: Leuconia johnstonii at World Register of Marine Species. Accepted name: Leuconia johnstonii Carter, 1871. AphiaID: 132200.

Classification: Biota; Animalia; Porifera; Calcarea; Calcaronea; Baeriida; Baeriidae; Leuconia

Voucher: BELUM : Mc1843. Strangford Lough, Down.

Editors: D. Moss, B.E. Picton.