Peremistocrinus from the Dewey Limestone Formation, Oklahoma

Extract

The first systematic study of anal variations found among various Carboniferous crinoids was presented by James Wright (Geol. Mag., lxiii, 1926) and covered Eupachycrinus calyx (McCoy) (now Phanocrinus Kirk) and Zeacrinus konincki Bather. Subsequently (Geol. Mag., lxiv, 1927), the genus Hydreionocrinus, and Ulocrinus globitlaris (Geinitz) (now Ureocrinus Wright and Strimple, Geol. Mag., lxxxii, 1945) were also considered. A total of 2,014 dorsal cups from the Scottish Lower Carboniferous (Mississippian) were involved in the examinations. These specimens were all from strata considered equivalent to the Chester Series (upper Mississippian) of North America. When presenting the genus Phanocrinus Kirk (Journ. Paleont., 11, 1937) recognized the importance of Wright's studies, but noted that examination of an almost equal amount of American material (primarily the Springer collection of the U.S. National Museum) had failed to disclose such great variations. That Kirk was highly impressed by Wright's studies is certain, for in personal conversations, several years ago, he emphasized the potentialities as they might affect my impending studies of Pennsylvanian crinoids. It has, therefore, been with much interest that I have watched similar patterns of development appearing in the large collections being made from both Chester (Upper Mississippian = European upper Lower Carboniferous) and Missouri (Middle Pennsylvanian = European middle Upper Carboniferous) of north-eastern Oklahoma.