Hallmann, 1917
Definition: Encrusting, massive or branching Halichondrida. Megascleres are monactinal (styles), diactinal (oxeas), or both, contained within widely spaced multispicular spongin fibres, or with little or no spongin associated, forming reticulate tracts, with poorly developed or no axial compression and poorly differentiated axial and extra-axial skeletons (disorganised-plumose). Microscleres are smooth or spined microxeas, often centrangulate or strongly bent at the centre (Halicnemia patera spics), and sometimes raphides in groups (trichodragmata) or singly, and in one genus acanthose cladotoxa and birotule-like spicules are also present.
Remarks: 14 nominal genera, of which 8 are recognised as valid. Review: Van Soest and Lehnert, 1997.
Source: Hooper's Internet Sponge Guide.
Genera represented in the area;
Halicnemia Bowerbank, 1862 (type species H . patera Bowerbank, 1862): encrusting, disk-shaped, with a very hispid surface; choanosomal skeleton consists of a basal layer of longitudinal spicule tracts lying on the substrate, including a halichondroid reticulation of styles and polytylote smooth oxeas; extra-axial styles or tylostyles are embedded and erect on this basal layer, protruding through and tangential to the surface; specialized ectosomal spicules consist of erect brushes of acanthose, centrangulate or straight, microxeas.
Higginsia Higgin, 1877 (type species: Higginsia coralloides Higgin, 1877) (syn. Dendropsis Ridley and Dendy, 1886; Desmoxya Hallmann, 1917): erect, lamellate, massive, vasiform or lobate growth forms; surface conulose, papillose, often silt covered; skeletal structure ranges from hlaichondrioid with a partially compressed, reticulate axis, and an irregularly plumo-reticulate extra-axial region (Higginsia), a compressed axis and a radial, non-plumose extra-axial region (Dendropsis), to a lax plumose or plumo-reticulate axial and extra-axial region, without axial compression or regional differentiation of the skeleton (Desmoxya); spongin fibres usually poorl developed although collagen in the mesohyl is heavy, usually with numerous megascleres and microscleres scattered between the main skeletal tracts; all skeletal tracts cored by monactinal and/or diactinal megascleres. Ectosome without specialised spiculation, but with extra-axial spicule tracts (1 or 2 categories of megascleres) protruding through the surface. Megascleres are oxeas, strongyles and/or styles of 1-3 sizes. Microscleres are spined, centrangulate curved or straight microxeas, sometimes also with raphides occurring singly or in bundles (trichodragmata).
Species included:
Halicnemia patera
Species not treated here:
Higginsia strigilata (Lamarck, 1814), Iceland, deep water