Class 11 NEET Biology Animal Kingdom Questions Part 1

(b) : The Phylum Porifera is divided into three classes : calcarea or calcispongiae, hexactinellida or hyalospongiae and demospongiae or sclerospongiae, on the basis of spicules (skeleton). Class Calcarea have calcareous spicules, Class Hexactinellida have siliceous spicules and Class Demospongiae have siliceous spicules or spongin fibres or both.