Coscinostoma fragilis
Schrammen 1910
The sample shown in the 2 figures to the left is now identified as Coscinostoma fragilis. (It has been mistaken previously for Verruculina astraea.)
Coscinostoma fragilis is very rare at Misburg. The sponge body tapers downward to form a relatively long stem. The pores on the outside wall are tiny and are surrounded by mm-sized dendrite-like furrows in the specimen shown. On the inside of the funnel, there are groups of small postica which are sourrounded by radiating furrows, forming large (up to 20 mm) star-like patterns. The wall thickness of the specimens known to the author is 6 to 8 mm and attains 10 mm in very large specimens (see below). In smaller individuals, the funnel margin may have an undulating outline.
The image to the left shows a detail of the star-shaped furrows typical of the species.
Picture of a very large (adult) individual of Coscinostoma fragilis. The funnel margin forms extensive lobes.