Eumastia sitiens Schmidt, 1870


Family : Halichondriidae

Form: Cushion-shaped with numerous upright papillae, some of the papillae have a terminal oscule. The papillae can be branched or singular. Size up to 15 cm across.

Colour: Pale yellow.

Consistency: Firm.

Surface: Surface smooth, papillae hollow, conical, stubby at the summit, or more tapering if they bear a terminal oscule.

Internal characters

Skeleton: Ectosomal skeleton a tangential "skin" of intercrossing bundles of oxeas; subdermal lacunae make the ectosome easily detachable. Choanosomal skeleton ill-defined spicule tracts and many loose single spicules; spicule tracts which may reach a diameter of 90 Ám. In the papillae longitudinal supporting fibres may be as thick as 1500 Ám.

Spicules: Exclusively oxeas, gradually tapering and sharply pointed, in a single but variable size category: 360-1020 x 7-20 Ám.

Habitat: On Pecten or other hard objects, 15-160 m.

Distribution: Norway, Iceland, Greenland, NE Canada.

Distribution Map: NBN map : National Biodiversity Network mapping facility, data for UK.

Identity: This species was originally described as Eumastia, but this was synonymized with Halichondria by Van Soest et al. (1990). The species is distinctive and cannot be easily confused with others in the area.

Editors: Christine Morrow, Bernard Picton & Rob van Soest.

 Picton, B.E., Morrow, C.C. & van Soest, R.W.B., 2011. [In] Sponges of Britain and Ireland