Lower Cretaceous crinoids from Texas

Small stemless highly ornamented crinoid calyces and free brachials are abundant in the Fredericksburg and Washita groups of the Lower Cretaceous of Texas. They are referred to a new family, the Roveacrinidae, and to six genera, four of which are new. The new genera are Discocrinus, Plotocrinus, Poecilocrinus, and Orthogonocrinus. The Roveacrinidae closely resemble the comatulids but, instead of cirri, possess horizontal and vertical flanges, spines, nodes, and corrugations. They developed from a stemmed ancester and became highly modified for a passive floating existence. The Roveacrinidae are excellent stratigraphic fossils. Species are widely distributed, easily identified, and have short vertical ranges. INTRODUCTION AND ACKNOWLEDGMENTS W ITH the exception of Uintacrinus socialis from the Niobrara of Kansas, crinoids have been considered a rarity in the North American Cretaceous. Biese and Sieverts-Doreck (1937) list only six species, three of which are represented by columnals only, and three by calyces. None of these is from the Lower Cretaceous. It was with considerable surprise, therefore, that I discovered in the spring of 1941 that small stemless calyces and free brachials occur literally by thousands in the Lower Cretaceous of