WORTHENIA

genus of extinct gastropods (snails) preserved as common fossils in rocks of Devonian to Triassic age (408 to 208 million years old) but especially characteristic of Late Carboniferous deposits (320 to 286 million years old) in the midcontinent region of North America. Worthenia is characterized by a turban-shaped shell in which a raised ridge follows the margin of the whorls. Small nodes occur along the ridge, and the opening of the shell is oval and large.