Practice question

Euplectella aspergillum commonly known as Venus' flower basket is elegant glass sponge belonging to Class Hexactinellida found in deep bathyal waters western Pacific below 500 meters. Its skeleton constitutes entirely siliceous spicules specifically hexactine triaxon type six rays orthogonal composed hydrated amorphous silica fused into three-dimensional lattice forming cylindrical basket-like cage with sieve plate covering osculum anchoring via basal tuft. Structure exhibits glassy appearance exceptional strength optical properties. No spongin or calcareous spicules present. Siliceous composition and hexactine symmetry distinguishes hexactinellids from Calcarea with calcareous spicules and Demospongiae with combination spongin and siliceous spicules historically defined for classification and identification.