Cornacuspongida

the largest order of sponges (Porifera). The skeleton consists of monaxon siliceous spicules and an organic substance, spongin, or only of spongin fibers. The canal system is of the leucon type. Most Cornacuspongida are colonial, with colonies having the form of crustlike or pillow-shaped growths or tubular, funnel-shaped, or bushy formations. The height of a colony is up to 0.5 or more. Cornacuspongida are found from the tidal zone to the ultra-abyssal zone. In the salt and fresh waters of the USSR there are about 220 species; representatives of the genera Halichondria, Haliclona, Hymeniacidon, Mycale, Myxilla, and Tedania are common.