Phorbas microchelifer (Cabioch, 1968) is a thinly encrusting sponge with an irregular surface. Life colour is unknown. It is very close to P. dives and P. bihamiger in spicule categories and dimensions. It is known only from a single record in the Roscoff area.
Colour: Life colour unknown; greyish in alcohol.
Shape, size, surface and consistency: Thinly encrusting, 1-1.5 mm thick on pebbles, bryozoans and barnacles. Surface bumpy, finely hispid.
Spicules: Megascleres: Ectosomal tornotes, inequiended ("tornostrongyles"): 140-190 x 1.5-2.5 µm; main acanthostyles, lightly spined on the upper half: 210-330 x 4-7 µm; echinating acanthostyles, entirely spined: 85-135 x 4-7 µm.
Microscleres: Arcuate isochelae: 12-20 µm (exceptionally: 24 µm); sigmata: 14-45 x 1-2 µm.
Skeleton: Plumose. Columns of acanthostyles traverse the choanosome and are echinated by the smaller category of acanthostyles. Tornotes are arranged singly or in bundles in the ectosomal membrane. The isochelae are concentrated in the ectosome, the sigmas are found throughout the sponge.
Ecology: Encrusting pebbles and other bother organisms at 30 m depth.
Distribution: Known only from the type locality Roscoff.
Type specimen information: The type is in the collections of the Station Biologique, Roscoff.
The distinctness of this species from closely related species, P. dives and P. bihamiger, remains doubtful. Cabioch compared the specimen with Phorbas dives, concluding that this has shorter principal acanthostyles, thicker tornotes and larger arcuate isochelae.
Source: Cabioch, 1968