Halichondria (Halichondria) agglomerans Cabioch (1968) is yellow cushion-shaped smooth sponge, showing subdermal canals under a shiny skin. It agglomerates sand and other bottom particles. This is a dubious species, distinguished from related sponges such as Halichondria (H.) panicea only by its longer oxeas which are more definitely divisible in two categories. It has been recorded only once in deeper water off Roscoff.
Shape, size, surface and consistency: Cushion-shaped with shiny surface. No size given. Ectosome detachable, over wide (1-2 mm) subectosomal canals. Interior cavernous, loaded with debris and sand. No information on apertures. No information on consistency but probably crumbly.
Spicules: Oxeas of all sizes between 275 and 830 x 4-19 µm; apparently these may be divided in two size classes: 275-350 and 525-830 µm.
Skeleton: Ectosomal: a tangential crust of intercrossing megascleres, leaving open spaces in which pores are concentrated. Choanosomal: confused, but some tracts are oriented towards the surface. Abundant debris is packed in the deeper parts of the sponge.
Ecology: Dredged at 75 m.
Etymology: The name refers to the agglutinating of sand grains by this species.
Type specimen information: The type is in the collections of the Station Biologique, Roscoff.
The specific distinctness of this material remains doubtful in the absence of clear differences with other Halichondria and Topsentia species. From the two common Halichondria species (H. (H.) panicea and H. (H.) bowerbanki) it differs in the upper size range of the oxeas.
Source: Cabioch, 1968.