Sponges without skeleton: A new Mediterranean genus of Homoscleromorpha (Porifera, Demospongiae)

A new genus of aspiculate homoscleromorph, Pseudocorticium, is described along with the new species P. jarrei found in a littoral cave located in the western Mediterranean Sea (France). The anatomy and cell composition are described and compared to that of species of the other homoscleromorph genus without skeleton, Oscarella, and to genera with skeleton, Corticium and Plakina. The new sponge differs from Oscarella in its morphology, anatomy, and cytology. An emended definition of the genus Oscarella is proposed. Anatomical and cytological characters carry a high informative content and should be described for a greater number of sponge species.