Clathria (Microciona) bitoxa (Burton, 1930a) is a thinly encrusting sponge belonging to the large group of Clathria (Microciona) species which can only be reliably identified by microscopic examination. It lacks chelae. It is known only from Scandinavian waters.
Colour: Pale brown in alcohol.
Shape, size, surface and consistency: Thinly encrusting, pores and oscules not apparent.
Spicules: Megascleres: Ectosomal subtylostyles, smooth, with a crown of small spines at the base: 600 x 5 µm; long styles, smooth: 900-1200 x 15 µm; small entirely spined acanthostyles: 60 x 5 µm. Microscleres: Toxas of two kinds, short stout, variable in size: 30-105 x 4 µm, and long hair-like forms: 150 µm.
Skeleton: Hymedesmoid: long styles and acanthostyles with their bases embedded in a basal plate of spongin; ectosomal subtylostyles form an irregular tangential layer at the surface. Small toxas scattered irregularly throughout the sponge; hair-like toxas forming wisp-like bundles.
Ecology: No data.
Distribution: Norway, West coast of Sweden.
Etymology: The name refers to the two kinds of toxas.
Type specimen information: BMNH 1910.1.1.787V (wet). Norman Collection.
The species was erected as member of a genus Hymantho Burton (1930) based on the absence of chelae. In view of the variability of the presence of chelae in the order Poecilosclerida, this genus is considered artificial. A second species of Clathria lacking chelae from Scandinavian waters is C. normani (Burton, 1930a), differing in having much smaller styles and only a single toxa category.
Source: Burton, 1930a.