R. D. Hoare

ECHINOCHITON DUFOEI: A NEW SPINY ORDOVICIAN CHITON

Abstract Echinochiton dufoei new genus and species is described from the Ordovician age Forreston Member, Grand Detour Formation (Blackriveran) near Beloit, Wisconsin. For a variety of reasons, we regard E. dufoei as a chiton; the species is known from four articulated or partially articulated specimens, one of which has eight plates and two of which have a mucro on the tail plate. Echinochiton dufoei differs from other chitons in having large hollow spines that project from each of the known plates. In plate shape and position, E. dufoei is much like the Upper Cambrian species Matthevia variabilis Walcott, 1885, and the Lower Ordovician species Chelodes whitehousei Runnegar, Pojeta, Taylor, and Collins (1979).

Bivalves (Mollusca) from the Imo Formation (Mississippian, Chesterian) of north-central Arkansas

The Chesterian Imo Formation in north-central Arkansas contains an abundant and diverse bivalve fauna which is dominated in numbers by nuculoids. The pterioids, pholadomyoids, and nuculoids show the greatest, and nearly equal, species diversity. Ecologically, on a generic level, the fauna is dominated by infaunal, burrowing, suspension feeders with attached suspension feeders a close second. Among the 40 taxa identified, the following new taxa are proposed: Economolopsis gordoni n. gen. and sp.; Spathelopsis browni n. gen. and sp.; Paleyoldia angustia n. sp.; P. bruta n. sp.; Phestia corrugata n. sp.; P. wortheni n. sp.; P. obtusa n. sp.; Imoella obscura n. gen. and sp.; Prothyris ( Lophoprothyris ) crista n. subgen. and sp.; Ectogrammysia crassatis n. gen. and sp.; Asketomorpha grandis n. gen. and sp.; and Sphenotus pisinnus n. sp. On the basis of ammonoids, the upper portion of the Imo Formation falls within the Elvirian Stage, E 2 b–c undifferentiated. Foraminifera place the formation in Mamet zone 19. The bivalve fauna discussed herein was collected from the E 2 b–c portion of the Imo.

New Carboniferous species of Hippocardia (Rostroconchia, Mollusca) from the Midcontinent, USA

Three new species of Hippocardia, H. ancora, H. pala , and H. cucullata , are described. Hippocardia ancora and H. pala occur together in the Lazy Bend Formation (Desmoinesian) of Texas. Hippocardia cucullata occurs in the Imo Formation (Chesterian) of Arkansas.

STRUCTURE, TAXONOMY, AND EPIFAUNA OF PENNSYLVANIAN ROSTROCONCHS (MOLLUSCA)

Abstract Reinterpretations are made of North American Pennsylvanian rostroconchs based on shell form, shell structure, and surface ornamentation. The new family Pseudobigaleaidae, new genera Baiosoma, Hadropipetta, Exalloschema, Oxyprora, and Apotocardium are erected, and the new species Arceodomus angustus and Apotocardium plautum are recognized. Study of growth increments on Apotocardium lanterna (Branson) indicate annual and monthly growth rates and life span. Thin sections studied provide insights into shell layer structure and thickness and variation in shell form. Characteristics of the protoconch and its relationship to body shell layers are illustrated. Epifaunal elements consisting of worm tubes, inarticulate brachiopods, acrothoracic barnacles, bryozoans, corals, and algae are present, some suggest attachment to the host rostroconch in life position.

PERMIAN POLYPLACOPHORA, ROSTROCONCHIA, AND PROBLEMATICA FROM OREGON

Abstract A silicified fauna from the early Permian Coyote Butte Limestone within the Grindstone terrane of central Oregon contains a diverse fauna including five polyplacophorans, one rostroconch, and one problematic taxa. New taxa include Gryphochiton planoplata new species, Arcochiton soccus new species, Homeochiton triangularis new genus and species, Arceodomus sphairikos new species, and Diadeloplax apiculatus new species.

Bivalves (Mollusca) from the Mauch Chunk Group (Mississippian, Chesterian) of northern West Virginia and southwestern Pennsylvania

A new genus, Novoameura, is erected with the type species Anisopyge mckeei Cisne. Delaria macclintocki Cisne from the Kaibab Formation of Arizona is herein regarded as a junior synonym of Delaria sevilloidia (Chamberlain), which was originally described from the Phosphoria Formation of Wyoming. The Leonardian (Permian) San Andres Formation of the Sacramento Mountains, central New Mexico, contains trilobite species known both from the Kaibab Formation of Arizona and the Phosphoria Formation of Wyoming, but lacks trilobite species known from the nearby Permian of West Texas.

THE PENNSYLVANIAN GASTROPOD DONALDINA KNIGHT IN THE APPALACHIAN BASIN, EASTERN U.S.A.

ABsTRAcr-Specimens of the gastropod genus Donaldina are numerous throughout marine units of the Pottsville, Allegheny, and Conemaugh Groups in the Appalachian Basin. Six species of Donaldina from thirteen marine units are described. New species proposed are Donaldina quadroliratus, from Pottsville and Allegheny units, and Donaldina superclivis, from Conemaugh units.

EUROPEAN PALEOZOIC POLYPLACOPHORA, MULTIPLACOPHORA, AND TURRILEPADIDA IN UNITED STATES REPOSITORIES

Abstract Three important collections of European Devonian and Lower Carboniferous polyplacophorans have been located in United States institutions. The specimens provided a basis for better description of important characters and clarified some taxonomic assignments. Two new polyplacophoran species are in the collections, Helminthochiton carpenteri from the Devonian of Germany and Pterochiton absidatus from the Lower Carboniferous of Belgium. Beloplaxus sagittalis (Sandberger and Sandberger, 1853–1855) is recognized as a multiplacophoran and a new genus and species of turrilepadid, Bouturrilipas scutatus, is proposed.

LOWER PERMIAN POLYPLACOPHORA (MOLLUSCA) FROM ARGENTINA

Abstract Several polyplacophoran plates are preserved as external molds in the Lower Permian Rio Genoa Formation, Chubut Province, Argentina. These are the first reported Permian polyplacophorans from South America. The new genus and species Asketochiton chubutensis is described based on this material.

THE OSTRACODE GENERA MOORITES CORYELL AND BILLINGS, 1932, AND DISCOIDELLA CRONEIS AND GALE, 1938, IN THE PENNSYLVANIAN OF THE APPALACHIAN BASIN

Rare to abundant specimens of Moorites Coryell and Billings, 1932, and Discoidella Croneis and Gale, 1938, have been recovered from 13 Pennsylvanian stratigraphic units in the Appalachian basin. Eight species of Moorites, including the new species M. sturgeoni, M. ornatus. M. percultus, and M. erugatus, are recognized. Discoidella is represented by D. lingulata Cooper, 1946. Moorites hewetti Coryell and Billings. 1932, is recognized as the type species of Moorites. An ontogenetic series of M. percultus illustrates changes in shape and ornamentation. Increase in complexity of ornamentation from Lower to Upper Pennsylvanian provides a basis for specific identification.