Diversity
There are about 400 described species of sponges in the Calcarea group.
- Wörheide, G. 2002. "Calcarea Introduction" (On-line). Gert Wörheide's homepage about geobiology. Accessed January 13, 2005 at http://wwwuser.gwdg.de/~gwoerhe/calcarea_introduction.html.
