A thin limestone tongue in the upper part of the Murdock Mountain Formation of northeastern Nevada contains abundant bryozoans of earliest Wordian age. This bryozoan fauna is close to the Kungurian-Kazanian boundary in Russia. These bryozoans are younger than those found in the Kaibab Formation of southern Nevada and slightly older than those in the Gerster Limestone of northern Nevada. This limestone tongue, herein referred to as the Stenodiscus beds, lies below the Thamnosia beds described by Wardlaw in the Murdock Mountain section of the Leach Mountains. This bryozoan-rich limestone tongue serves as a marker unit for mapping the Murdock Formation in the Leach Mountains.

Nine new species of bryozoans occur in the Stenodiscus beds of the Murdock Mountain Formation: Hinganella felderi, Neoeridotrypella schilti, Stenopora parvaexozona, Stenodiscus murdockensis, Dyscritella acanthostylia, Pseudobatostomella irregularis, Streblotrypa (Streblotrypa) elongata, Morozoviella praecurriensis, and Thamniscus erraticus, Hinganella felderi, Neoeridotrypella schilti, Dyscritella acanthostylia, and Streblotrypa (Streblotrypa) elongata are very similar to species described from Russia.

Protorthacean brachiopods from the Middle Cambrian of the Moroccan Atlas regions are described in terms of morphology and systematic affinities. The superfamily Protorthacea is revised to include both Protorthidae and Bohemiellidae. Newly introduced is the protorthid genus Saesorthis, the morphologic characteristics as well as the significance of which are discussed in detail together with their bearing on early phylogeny of the Orthacea. A reinvestigation of Brahimorthis antiqua led to the recognition of additional morphologic peculiarities and enhances understanding of its stratigraphic occurrence. Additional descriptions and discussions deal with informally described protorthid and bohemiellid species. Bohemiella and Jamesella are reported from Africa for the first time.

In the Lower Devonian the first productellids evolved from their chonetidine ancestors as the Productellinae. This subfamily was the stem group from which all the later Productidina evolved, yet three of its five subfamilies persisted to the end of the Permian. The main characters used in the new classification, here presented, for the Productellidae are described and reviewed, and the main changes seen during its evolution are discussed. Within this new classification five new genera are described: in the Overtoniinae are Barunkhuraya Lazarev from the latest Famennian, Onavia Lazarev from the Tournaisian, both from Mongolia, and Echinariella Lazarev (type species Krotovia jisuensiformis Sarycheva) from the late Permian of Transcaucasia; in the Marginiferinae there is Breileenia Brunton from the Visean of western Europe and in the Plicatiferinae is Maemia Lazarev from the mid and Upper Carboniferous on the coast of the Barents Sea. New species described in these genera are Barunkhuraya indrengynensis Lazarev, Onavia barunkhurensis Lazarev, Breileenia radiata Brunton, Maemia chaykensis Lazarev, and M. nana Lazarev.

A single specimen of Hazelia palmata Walcott, 1920, was collected from the Middle Cambrian Marjum Formation near Marjum Pass, in the central House Range, western Utah. This is a first occurrence of the species outside the Burgess shale region of British Columbia, Canada. The flattened oval impression of the monaxonid demosponge shows characteristic tufts and spicule structures of the species.

Cardiarina cordata Cooper, 1956, has previously been placed in the Rhynchonellacea. Specimens present in the Dickerson Shale (Pennsylvanian, Desmoinesian) in north-central Texas have a terebratulid centronelloidiform loop, and although there are no punctae preserved, are questionably assigned to C. cordata and placed in the Terebratulacea.

Epistreptophyllum cornutiformis Gregory, 1900, is the name assigned to a Middle Jurassic population of scleractinian corals from Kachchh, western India. Measurements of ten variables from 84 specimens of this population have been statistically examined by means of univariate and multivariate analyses. A wide range of variation in corallum shape, septal perforation, lateral septal surface ornamentation, nature of the endotheca, and that of the columella is observed. The great majority of specimens are solitary. The wide range of gradational variation observed in this population corresponds to and includes the morphological characters described for various scleractinian genera such as Protethmos Gregory, Metethmos Gregory, Frechia Gregory, and Epistreptophyllum Milaschewitsch. The assignment of these genera to this later senior synonym genus is supported by the description of a well-preserved topotype from Nattheim. The ornamentation of the septa in Epistreptophyllum is detailed and distances it from typical pennular corals.

Shell-encrusting assemblages have uniquely high ecological fidelity among paleocommunities because adjacent epibionts coexisted in ecological time, and the abundances and spatial relationships of the various members are accurately preserved. This study presents a quantitative reconstruction of communities on brachiopod shells (Composita and alate spirifers) from the Carboniferous of North America. Thirty-one epibiont communities, comprised of a total of 1180 encrusted brachiopods, are analyzed in terms of epibiont abundance (e.g., percent areal cover), ecological diversity (e.g., Shannon-Wiener Index), and the role of larval recruitment and spatial competition in structuring the communities.

Mississippian epibiont communities contain from seven to 14 encrusting taxa that occupy up to 25 percent of host shell surfaces. These communities are spatially dominated by trepostome bryozoans, but also include common lower Paleozoic epibionts, such as encrusting ctenostome bryozoans, hederellids, cornulitids, and edrioasteroids. Pennsylvanian epibiont communities contain between eight and 16 epizoan taxa that occupy up to 34 percent of shell surfaces. They are dominated by fistuliporoid or trepostome bryozoans and increasing proportions of erect bryozoans (e.g., fenestellids), encrusting foraminiferans, and articulate brachiopods.

Carboniferous epibionts, like their modern counterparts, exist in loosely organized ecological communities that vary widely in abundance and composition in space and geological time. There is little evidence for tight controls on community structure. Much of the variation is attributed to vagaries in the magnitude and selective nature of larval recruitment. Evidence of competition between community members is rare, except where a high percentage of the shell surface is covered. In these cases, sheetlike bryozoans are usually most abundant. Solitary epibionts are surprisingly successful competitors in one-on-one encounters, but apparently lose areal cover to longer-lived colonial encrusters during ecological succession.

Shell structure has been studied in two species of the family Craniidae Menke, 1828, from the Upper Jurassic of East Ukraine and from the Lower Cretaceous of Crimea, South Ukraine. These species belong to the new genus Mesocrania—M. barskovi (Smirnova, 1972) and M. condylata new species. A layer of coarse regular rhomboidal crystallites was discovered between the primary layer of acicular crystallites and the secondary laminar layer. Branching punctae canals were observed in M. barskovi.

“Lingulepis’ malongensis Rong from the upper part of the Lower Cambrian Chiungchussu Formation of Yunnan is referred to Lingulellotreta Koneva; L. malongensis (=Lingulellotreta ergalievi Koneva) is redescribed on the basis of new material from the Lower Cambrian of south Kazakhstan. It is the earliest known taxon of the Lingulellotretidae, which is unique within the Linguloidea in having an elongate pedicle foramen and internal pedicle tube. The occurrence of Lingulellotreta malongensis in south China is considered usually to be of Atdabanian age, but brachiopod based correlation with south Kazakhstan suggests that a possible Botomian or younger age, for both the upper part of Chiungchussu Formation in Yunnan and the lowermost part of Shabakty Group in the Malyi Karatau Range, is equally plausible.

Two occurrences of Middle Ordovician opercula belonging to the gastropod Maclurites are described, one from the Taimyr Peninsula, Siberia, and one from the Kuskokwim Mountains, Alaska. The Taimyr opercula are the first to be described from Russia. Like other opercula of the genus, these thick specimens have a relatively massive prong on the interior to which the retractor muscle was attached. The Alaskan specimens preserve a secondary muscle attachment site. The described occurrences of Maclurites opercula are summarized.

Famatinorthis cf. F. turneri Levy and Nullo, 1973, is an abundant component of a poorly preserved brachiopod assemblage in volcaniclastic rocks at one locality in the Arenig-age Shin Brook Formation in northeastern Maine. The brachiopod assemblage of the Shin Brook Formation has been classed as a Celtic biogeographic assemblage that is interpreted to have lived in cool water at mid- to high peri-Gondwanan latitudes. Famatinorthis turneri sensu stricto is one of the six brachiopod species known from coeval volcanicsrich rocks of continental margin affinities in the Famatina Range of northwestern Argentina; the presence of its congener in Maine supports the Celtic affinities of the Famatina assemblage, but its Ordovician location remains cryptic.

Odontopleurids are a diverse component of rich silicified trilobite faunas recovered from the Wenlock and Ludlow of the Cape Phillips Formation, central Canadian Arctic. Odontopleurinae and Acidaspidinae are common, but Ceratocephalinae and Koneprusiinae are also represented. This work treats all of the Odontopleurinae, with the exception of the genus Acanthalomina Prantl and Přibyl, 1949.

New species of Kettneraspis Prantl and Přibyl, 1949, include the upper Sheinwoodian K. wrightae, the lower Homerian K. lindoei, and the Gorstian K. caldwelli. Rare specimens assigned to Odontopleura Emmrich, 1839, and Radiaspis Richter and Richter, 1917, occur in the Sheinwoodian of the central Arctic.

Edgecombeaspis (type species E. johansonae new species) is proposed for an odontopleurine clade endemic to Laurentia, and in the Silurian restricted to northern Laurentia. Cladistic analysis yields a hypothesis of ingroup structure that is in general calibrated with stratigraphic sequence. An exception is a group of Telychian species from the Mackenzie Mountains, whose stratigraphic sequence was used to support a previous hypothesis of an ancestral-descendant lineage. The cladistic result indicates that the stratigraphic pattern is the inverse of the phylogenetic pattern: the stratigraphically lowest species in the proposed lineage is the most derived, and the highest is most primitive. In addition to the type, new species of Edgecombeaspis include the mid-Sheinwoodian E. jahansi and the lower Homerian E. soehni. Edgecombeaspis apparently became extinct in the Homerian.

The species Kettneraspis lenzi (Chatterton and Perry, 1983) and Radiaspis cf. R. norfordi (Chatterton and Perry, 1983) occur in the central Arctic, and further strengthen previous correlations with strata in the central Mackenzie Mountains, Northwest Territories.

All previously known late Ordovician and Silurian trimerellides of Kazakhstan are reviewed and reillustrated, together with some recently discovered taxa, including the late Caradoc-Ashgill Palaeotrimerella medojevi new species from the Chu-Ili Range, the late middle Ashgill Gasconsia cf. worsleyi Hanken and Harper, and Silurian Dinobolus cf. hubeiensis Rong and Yang, both from Central Kazakhstan. Kazakhstanian terranes appear to contain the oldest-known trimerellide faunas from late Llandeilo to early Caradoc. The observed geographic distribution of Ordovician trimerellides may be explained as the result of two major migrations from the Kazakhstanian terranes: 1) during the early Caradoc, to Gondwana and North America; 2) during the late Caradoc, to Baltica and Angaria. All local trimerellide lineages in Kazakhstan became extinct just before the Hirnantian, and were replaced in the Llandovery by new forms, probably of Chinese origin.

Five species of nuculoid bivalves are described from Pennsylvanian outcrops of the Ixtaltepec Formation, Oaxaca, Mexico: Nuculopsis sp., Palaeoneilo sinuosus new species, Paleyoldia sp., Phestia bellistriata, and Phestia sp. have been collected in clastic rocks and in association with other marine invertebrate groups, which represent a peri-reefal environment.

This paper describes Byzantia obliqua, new genus and species. Byzantia is a small, distinctively ornamented, gastropod genus from the middle Permian (Leonardian-Guadalupian) of West Texas. This provides further evidence of the diversity of the Neritacea in the middle Permian and of the diverse endemic fauna of west Texas.

The Mazon Creek Cycloidea contain four taxa: Cyclus americanus Packard, 1885, Cyclus obesus, new species, Halicyne max, new species, and Apionicon apioides, new genus, new species. We conclude, based on a cladistic analysis, that cycloids are specialized maxillopodan crustaceans and a possible sister group to the Copepoda. They may have filled a niche similar to modernday crabs.

Repaired shell injuries are reported in 11 specimens including six genera and eight species of gastropods from the upper Middle Ordovician (Caradoc) Kullsberg Limestone and the Upper Ordovician (Ashgill) Boda Limestone, Siljan district, Sweden. The specimens are of different sizes and morphologies, including one isostrophic, three low-spired, and six moderately high-spired turbinate forms. Single and repeated episodes of shell damage and subsequent repair are preserved, the breaks ranging from simple arcuate or scalloped fractures to removal of large sections of the apertural margin. Both early and late growth stages show damage, but the injuries are usually restricted to only one whorl. No shell repairs were discovered on the 65 more or less complete specimens of the subulitids, although the smooth shell makes observation difficult. Injuries in the Siljan samples are found in both microgastropods and large specimens, but the sample is too small for meaningful quantification. The shell repair frequency is about 7 percent, based on examination of 404 specimens (54 from Kullsberg Limestone and 350 from Boda Limestone). Most of the repaired injuries are attributed to failed predation, adding significantly to the Lower Paleozoic documentation of predation on gastropods. The gastropod shells are morphologically weak by modern standards, but do show some architectural strengthening features such as narrow apertures, collabral or spiral threads, and other ornamentation. The identity of the predator(s) is unknown.

Restudy of Strophomena cornuta Hall, 1843, confirms that it belongs to the superfamily Chonetoidea and establishes its assignment to Strophochonetes within the family Strophochonetidae. This is the first recorded occurrence of the genus in the Silurian of New York, and its late Llandovery age makes S. cornutus (Hall) one of the earliest representatives of the genus.

Basal strata of the Tucumcari Formation south of San Jon, New Mexico, contain a bivalve assemblage different from that of the remainder of the formation. Ceratostreon texanum and two new species herein described (Gyrostrea hinchada, Plicatula quayensis) are the dominant faunal elements of these basal strata. A fourth bivalve, long known as Lopha quadriplicata, ranges downward approximately to the upper limit of C. texanum. However, reevaluation of the taxonomy of this and related species indicates that 1) they have little in common with typical representatives of Lopha and are grouped in a new genus, Peilinia, and 2) specimens from the Tucumcari and related formations formerly assigned to L. quadriplicata are a separate new species, P. levicostata, which appeared in the southern Western Interior before P. quadriplicata appeared in eastern Texas and Oklahoma. The biostratigraphic ranges of several widely distributed bivalves are utilized with ammonite range zones to refine the correlation of several southern Western Interior sequences with the classic lower Washita sequence of Texas and Oklahoma. Because ammonites are rare in the western area, bivalves are locally more important in establishing the age of some exposures. For example, the boundary between or slight overlap of the successive zones of C. texanum and P. levicostata in eastern New Mexico and west-central Texas marks the position of the Craginites serratescens ammonite zone to the east. Strata previously called Kiamichi and Duck Creek in west-central Texas are best considered part of the Tucumcari Formation, representing deposition that occurred mainly earlier than the main Tucumcari sequence in New Mexico.