TY - CHAP AB - Recent Lithonida (Calcarea, Calcaronea) contains two families of Calcaronea characterized by a hypercalcified skeleton, which is reinforced either by the linkage of tetractines or by the formation of a rigid basal mass of calcite. The living tissue has free calcareous spicules, most frequently including tuning-fork triactines, or diapasons. They appear as survivors of fossil ‘pharetronids’, a polyphyletic grouping of fossil calcareous sponges, and are presently restricted to submarine caves and to bathyal rocky environments. The fossil genera are not treated here. A1 - Vacelet, J. A1 - Borojevic, R. A1 - Boury-Esnault, N. A1 - Manuel, M. DO - 10.1007/978-1-4615-0747-5_121 N1 - The PDF supplied here is a proof - NOT the definitive printed text - of a chapter of the Systema Porifera C1 - ISBN 0-36-47260-0 (printed version) TI - Order Lithonida Vacelet, 1981, Recent. Pp. 1185-1192. In: Hooper, J.N.A. & Van Soest, R.W.M. (eds) Systema Porifera. A guide to the classification of sponges. (2 volumes) Kluwer Academic/ Plenum Publishers: New York, 1708 + xlviii UR - https://vliz.be/vmdcdata/narms/narms.php?p=sourcedetails&id=9094 PY - 2002 Y2 - 2024-03-28 ER -