Bathymetric distributions of Calcarea and Hexactinellida in the present and the past

Abstract

SUMMARYCalcarea and Hexactinellida are now characteristic of different depth zones, and have shown comparable bathymetric zonation since the Carboniferous period. This paper reviews and discusses relevant evidence from modern and fossil sponge faunas, together with some problems involved in the use of the modern data for the assessment of past depths. The most important independent evidence is provided by calcareous algae and herma-typic Scleractinia.