Crinoids of the disparid family Myelodactylidae are distinctive in having a bilaterally symmetrical distal column which was coiled in life, and a slender proxistele that is doubly recurved. Seven genera of myelodactylid have been described. Of these, Herpetocrinus is regarded as a junior synonym of Myelodactylus. Six species of myelodactylid are definitely recognized from the Silurian of Britain and Ireland: Myelodactylus ammonis (Bather), Myelodactylus fletcheri (Salter), Myelodactylus parvispinifer (Brower), Myelodactylus hibernicus sp. nov., Myelodactylus penkillensis sp. nov., and Myelodactylus sp. A. Myelodactylus convolutus Hall is not found in the Wenlock Limestone, despite reports to the contrary. Most myelodactylids, apart from the genus Crinobrachiatus, probably lay on the substrate on their sides.