Form: A thin (to 0.5mm) crust overgrowing rock surfaces, with an uneven, bubbly appearance. The spicules penetrating the surface may trap silt.

Colour: Vivid red.

Smell: None.

Consistency: Hard to describe since a very thin crust.

Surface: Villose, with long fine styles and shorter fine oxea penetrating the surface.

Apertures:

• Scattered, inconspicuous. Oscular rims are transparent with small blobs of red tissue.

Contraction:

• None.

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Internal characters

Skeleton: Eurypon spp. all have skeletons with a basal layer of acanthostyles perpendicular to the substrate and with their heads resting on the substrate. Very long tylostyles, also perpendicular to the substrate with heads in the basal spongin layer, are scattered amongst the acanthostyles. Where these tylostles penetrate the surface they are echinated by a brush or fan of fine styles or oxea. In Eurypon major these echinating spicules are fairly stout oxea, occasionally with rounded proximal ends.

Spicules: Tylostyles 1440 μm - 2210 x 10-17 , entirely spined acanthostyles ca. 85-165 μm (? up to ca. 125 μm - 164 μm). Ectosomal oxea measure ca. 385-525 x 3-7 μm.

Identity: All Eurypon spp. are thin crusts and several are red. Eurypon and Hymeraphia stellifera can be distinguished from other red crusts by the very long tylostyles that project 1 to 1.5mm through the surface. Eurypon major is the only Eurypon with abundant thick oxea present in the surface, and the dimensions of these oxea distinguish this species from Eurypon lacazei.

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

iNaturalist: Eurypon major at iNaturalist World Species Observations database.

WoRMS: Eurypon major at World Register of Marine Species. Accepted name: Eurypon major Sarà & Siribelli, 1960. AphiaID: 133115.

Classification: Biota; Animalia; Porifera; Demospongiae; Heteroscleromorpha; Axinellida; Raspailiidae; Raspailiinae; Eurypon

Voucher: BELUM : Mc1338. Lough Hyne, Cork.

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