Cretaceous sponges from the Campanian of Misburg and Höver
cf. Placonella perforata
The specimen shown here resembles very much the figure and the description given by Hinde (1883) for Placonella perforata, except that a 15 mm wide and 20 mm deep cavity (paragaster ?) exists. Besides this, the upper and lower surfaces of the depicted specimen show about 20 smaller (5 - 10 mm) pits.
The scleres are megaclones and the skeleton resembles that of Doryderma species.
Placonella perforata is a sessile (rootless) cake-like or lumpy sponge, described by Hinde (1883) from the Upper Jurassic of Nattheim, Southern Germany. Hinde notes the similarity to the genus Megalithista (Zittel), also known from the Jurassic system, and he mentiones that the two are distinguished only by the existence of a central cloaca in Megalithista.