a class of extinct invertebrates of the phylum Echinodermata. The Eocrinoidea lived during the Cambrian and Ordovician. The ambulacral system was primitive. The skeleton consisted of a theca, brachioles, and usually a leg or stalk, which served to attach the animal to substrates. The mouth was located at the top of the theca, and the anal orifice was to its side. The brachioles caught particles of food, which moved along the groove, to the theca and into the mouth. Pores located on the borders of the plates of the theca apparently served for respiration.
The Eocrinoidea were found throughout almost the entire world in the early Paleozoic seas, but their remains are found relatively rarely. The approximately 30 genera embrace 50 species, primarily from deposits in Europe and North America. In the USSR, remains have been found in Cambrian deposits in Yakutia and in Ordovician deposits in Leningrad Oblast and Estonia.
REFERENCESOsnovy paleontologa: lglokozhie. . . Moscow, 1964.
Treatise on Invertebrate Paleontology, part S, vol. 2. New York, 1966.
IU. A. ARENDT