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"Simple sponge (Ascetta primordialis). Note the vase-like form, the apical osculum, the inhalant pores in the walls." -Thomson, 1916

A. Primordialis

"Simple sponge (Ascetta primordialis). Note the vase-like form, the apical osculum, the inhalant pores…

Part of the outer wall of this Calcolynthus is cut away. This is a simple sponge.

simple sponge

Part of the outer wall of this Calcolynthus is cut away. This is a simple sponge.

Calcolynthus primigenius, a simple sponge with the wall removed to show the inside. It is hollow, attached at the base with an opening at the top. There are many small holes though the wall with water constantly entering and passing out through the mouth at the top.

Sponge

Calcolynthus primigenius, a simple sponge with the wall removed to show the inside. It is hollow, attached…