Pseudosuberites mollis Topsent, 1925b is a thin yellow encrusting sponge, with a detachable skin. It is similar to the closely related P. sulphureus but differs in having smaller and thinner spicules with slightly different morphology (microscopic examination). It is a southern species, known predominantly from the Mediterranean, but recorded a few times from the west coast of France.
Colour: Pale yellow.
Shape, size, surface and consistency: Thinly encrusting with smooth transparent surface; no size recorded. Skin easily detachable in flakes. Oscules not recorded. Consistency rather soft, easily damaged.
Spicules: Tylostyles, often with indistinct tyle, normally slightly below the end, occasionally there is a double tyle, the end of the spicule above the tyle is as wide as below the tyle: 175-365 x 6-8 µm
Skeleton: Detachable ectosome, consisting of a tangential crust of intercrossing bundles of tylostyles. Choanosome thoroughly confused, halichondroid, and with low spicular density.
Ecology: On rocks at 0-15 m.
Distribution: W coast of France: Iles de Glénan, Roscoff, estuary of the Rance; Mediterranean.
Etymology: The species is softer than its congeners.
Type specimen information: The type is in the Muséum National d'Histoire Naturelle, Paris.
The resemblance with P. sulphureus is considerable, but the larger spicules (up to 500 x 10 µm), and especially the mucronate tyles, make distinction possible. Both species are sympatric over a large part of their range.
Source: Topsent, 1925b.