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Hexactinellida

Hexactinellida (Hyalospongea; phylum Porifera) A group of sponges that first appeared in the Cambrian. They are of normal sponge shape and have skeletal spicules consisting of opaline silica. Large spicules (megascleres) and small spicules (microscleres) are connected in various patterns, and this forms the basis for the classification of the group. They were common in the Palaeozoic but many forms disappeared in the Permian. They were again important in the Jurassic and Cretaceous, but are now confined to much deeper marine waters.

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"Hexactinellida." A Dictionary of Earth Sciences. . Retrieved May 29, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/hexactinellida

Hexactinellida

Hexactinellida (Hyalospongea; phylum Porifera) A class of sponges whose skeleton is composed of mainly six-rayed, siliceous spicules. Organic fibres do not occur. The body has a leucon structure. They are marine, deep-water sponges and first appeared in the Lower Cambrian.

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"Hexactinellida." A Dictionary of Zoology. . Encyclopedia.com. 29 May. 2017 <http://www.encyclopedia.com>.

"Hexactinellida." A Dictionary of Zoology. . Encyclopedia.com. (May 29, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/hexactinellida-0

"Hexactinellida." A Dictionary of Zoology. . Retrieved May 29, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/hexactinellida-0