Lower carboniferous sponges from the Craven Reef Belt of North Yorkshire

Fossil sponges are significant elements in framework facies of Late Visean Cracoean reefs of northern England. In the Craven Reef Belt (North Yorkshir e), lithistid demosponges, including Scheiia castletonense (Wolfenden 1959) , Haplistion carbonaria (Wolfenden 1959) and Haplistion mega sp, nov., occu r along with the less abundant, sphinctozoid demosponge Sollasia ramosa sp. nov, in this facies. Scheiia castletonense is an irregular globose to moun d-shaped tricanocladinid hindiid sponge with irregular secondary branchlike growths in which the canal and skeletal structure are continuous with thos e of the globular part of the sponge. Both species of Haplistion are rhizom orinid lithistid sponges. Haplistion mega is a lobate sponge characterized by moderately coarse skeletal tracts that are relatively far apart, in cont rast to the fine tracts and closer spacing in the more common globose to su bspherical Haplistion carbonaria. The aporate 'sphinctozoan' Sollasia ramos a, commonly appears in the available sections as isolated spherical chamber s because of its relatively loose branching habit and the beadlike to monil iform series of spherical chambers in each branch.