Tommotiids are a geologically short-lived group of early skeletal fossils, most abundant in the Lower Cambrian. Redescriptions of a lapworthellid (Lapworthella rete Yue, 1987) and a tannuolinid (Tannuolina zhangwentangi Qian and Bengtson, 1989) from the Jiulaodong Formation, Maidiping, Sichuan, augment previous accounts. Lapworthella rete approaches the L. dentata–L. schodackensis complex, but has a prominent external pattern of polygons that probably represent imprints of epithelial cells. Description of Tannuolina zhangwentangi emphasises ultrastructural features, including the mode of growth, development of canals, and possible epithelial imprints on the interior surfaces. Data on size variation of epithelial imprints in tommotiids are reviewed to try to infer possible variations in genome content of the cells. In addition, poorly preserved lapworthellids (Lapworthella sp.) are described from the Qiongzhusi Formation, Meishucun, Yunnan.

Six species belonging to the families Proporidae and Plasmoporidae occur in the Lower and Upper Silurian rocks of the Limestone Point and La Vieille Formations of northern New Brunswick and of the Anse à Pierre-Loiselle, La Vieille, and Gascons Formations of the Gaspé Peninsula of Québec. The three species of Propora are widely distributed but show varying faunal affinities, while both species of Plasmopora, Plasmopora logani and Plasmopora corrugata, are new and are almost endemic. Revised concepts of Propora and Plasmopora are proposed. The holotype specimen for the type species of Camptolithus was examined and confirms the genus as distinct from Propora, rather than a synonym as has been previously suggested.

The facies distribution of these corals is variable. In general, the proporids, which mostly occur in facies indicating shallow carbonate banks and patch reefs, are more restricted in distribution than the plasmoporids, which occur in these facies and also in others representing a variety of open-shelf environments.

The genus Bimuria Ulrich and Cooper, 1942, is a biogeographically important member of middle and late Ordovician brachiopod faunas of the Callahan–Gazelle area in the eastern Klamath Mountains of northern California. In middle Ordovician deposits the genus is widespread and ranges from Nevada in the west to southwestern Siberia in the east; however, in late Ordovician beds it was previously known only in Sweden and Northern Ireland. In addition to the northern California occurrence reported here, new late Ordovician occurrences are also noted in east-central Alaska–Yukon Territory and Northwest Territories. Three species of Bimuria are described, including the new species, B. californiensis.

A preliminary survey of species described in the literature suggests that the ratio of the length of the dorsal adductor field to the length of the elongate area in the brachial valve decreases from middle to late Ordovician species, and thus may be of biostratigraphic value.

Among the abundant, well-preserved rhynchonellid brachiopods in the Upper Ordovician–Lower Silurian rocks of Anticosti Island, Fenestrirostra Cooper, 1955, one of the earliest camarotoechiid genera to appear in the fossil record, is probably of oligorhynchiid ancestry and seemingly endemic to the Anticosti Basin. The genus differs most obviously from other camarotoechiids in its peculiar costae, which are angular and strong posteriorly and flat and weak anteriorly.

Three successive species of Fenestrirostra, found in micritic mudstones and calcareous shales of the middle and upper Merrimack and Lower Gun River Formations, provide an example of gradualistic evolution. The most primitive species, F. primaeva, occurs only in the lower part of the middle Merrimack Formation; the descendant intermediate species, F. glacialis, occurs mainly in the upper part of the middle and in the upper Merrimack and in the lowermost Gun River Formations; and the descendant terminal species, F. pyrrha, occurs only in the lower Gun River Formation. Four major morphoseries distinguish the lineage: 1) change in the proportions and size of the shells; 2) increase in the number and concomitant loss of the costae from the anterior halves of the shells; 3) change in the orientation and reduction in the size of the hinge plates and hinge fossettes; and 4) change in the height of the median septum. The evolutionary modifications, estimated to have been accomplished in no more than 1 m.y., may have been adaptive responses to persistent low-energy marine conditions.

Biostratigraphically, the Fenestrirostra lineage provides the basis for three interval or range zones that straddle the Rhuddanian–Aeronian interstage boundary in the Anticosti Basin.

A fragmentary and probably immature polyplacophoran shell from the Middle Triassic Germanic Muschelkalk is presented. Morphological peculiarities of the specimen are a stiff connection of the head valve to the adjoining intermediate valve and the presence of a yet undescribed brim-like shell constituent, informally called border-plate herein. The unusually well-preserved shell structure is discussed in detail comprising tegmentum, crossed-lamellar p. hypostracum and the (articulamental?) border-plate. Characteristics indicate a systematic position within the order Lepidopleurina.

The hyolithid species Hyolithes crebescens Resser and Endo, Hyolithes cybele Walcott, and Hyolithes delphus Resser and Endo from the Middle Cambrian of China are assigned respectively to the genera Nevadotheca Malinky, Novakotheca n. gen., family Hyolithidae, and Crestjahitus Syssoiev, family uncertain, all in the order Hyolithida. Recognition of Nevadotheca extends its geographic range from North America to China, and the occurrence of Crestjahitus in the Middle Cambrian of China increases its geographic and stratigraphic distribution from the Early Cambrian of the Soviet Union.

Poor preservation of the type specimens of Hyolithes? aliger Resser and Endo, H.? aplatus Resser and Endo, H.? cariniferus Resser and Endo, H.? daphnis Walcott, H.? delia Walcott, H.? endoi Howell (as H. ornatus Resser and Endo), H.? mantouensis Resser and Endo, and H.? tenuis Resser and Endo renders their generic identification uncertain. Hyolithes (Orthotheca) glabrus Resser and Endo is here transferred to the hyolith order Orthothecida Marek and referred with question to Decoritheca Syssoiev, family Novitatidae.

Morphology of the types of “Hyolithes” fuchouensis Resser and Endo, “H.” kuantungensis Resser and Endo, “H.” sondai Resser and Endo, “Orthotheca” daulis Walcott, and “O.” doris Walcott does not support assignment to the Hyolitha for these species; their phylogenetic affinity is uncertain.

Re-examination of some North American collections of the late middle to early late Norian pterioid bivalve Monotis confirms the separation of M. (M.) alaskana Smith from the European type species M. salinaria (Schlotheim). The related M. (M.) haueri Kittl, as differentiated statistically, is more widely represented in southern Alaska, the Canadian Yukon, and Nevada than was formerly recognized. Species described originally from northeastern USSR and now confirmed as present in rocks from Alaska and western Canada include: M. (Entomonotis) pachypleura (Teller), M. (Eomonotis) daonellaeformis Kiparisova, and M. (E.) anjuensis Bytschkov and Efimova. Monotis subcircularis Gabb and related forms are transferred from the subgenus Entomonotis to the new subgenus Pacimonotis in order to give the former subgenus a more homogeneous morphologic range.

Re-evaluation of the stratigraphic occurrences of these species shows that M. alaskana occurs above M. subcircularis and below M. haueri in the Wrangell Mountains, Alaska. Elsewhere in North America, however, Monotis haueri occurs at the same level as M. subcircularis and is thus a long-ranging form. These three taxa, as well as M. pachypleura, are representative of the upper Norian Cordilleranus Zone. Monotis daonellaeformis is among the oldest Monotis species of the middle Norian Columbianus Zone; M. anjuensis in North America is probably also from the Columbianus Zone but could overlap in occurrence with the upper Norian M. subcircularis.

Up to four discrete protaspid larval stages are described for calymenid trilobites of Ordovician to Devonian age. The earliest growth stages are nonadult-like planktonic protaspides; later protaspides are adult-like and benthonic. In contrast, the related homalonotid trilobites apparently lack planktonic protaspides, but have up to two large benthonic protaspid stages that are similar in form to calymenid benthonic protaspides. These differences in life history patterns between these families are reflected in their paleobiogeographic distributions. Calymenids werre widely dispersed from Ordovician to Devonian times, both being common in warm, low latitude provinces (particularly from the Late Ordovician onwards) and well represented in cooler, higher latitude regions. The paleogeographic distribution of the homalonotids during the Ordovician (Arenig to the Ashgill) was concentrated in high paleolatitudes, with only a few forms occurring at low paleolatitudes (often in deeper, cooler environments?). Both families survived the Ordovician–Silurian mass extinction, with the calymenids again being widely dispersed but the homalonotids being best represented in the cool-water Malvinokaffric Province and in other regions where they are largely restricted to clastic facies.

So few complete growth series of calymenine trilobites are known that it is unlikely that the ontogenies of taxa that form parts of ancestor–descendant clades can be identified. However, some evidence for heterochronic, particularly paedomorphic (neotenic), evolution is suggested for larval stages of members of both the Calymenidae and the Homalonotidae. Such possible neotenic evolution leading to very large planktonic larval stages of calymenid trilobites during the Devonian could have enhanced dispersal during a period of widespread warm and equable climates. Comparisons of homalonotid protaspides with equivalent stages of calymenids support the close relationship of these families within the Calymenina. A data matrix based upon characters of protaspides of two calymenine trilobites (Flexicalymene Shirley, 1936, and Brongniartella Reed, 1918) and eight other trilobites, belonging to the Phacopina (Calyptaulax), Cheirurina (Physemataspis and Hyrokybe), Proetida (Scharyia), Lichida (Acanthopyge), Odontopleurida (Diacanthaspis), Corynexochida (Bathyuriscus), and Ptychopariida (Crassifimbra) was subjected to cladistic analysis using the parsimony program “Hennig 86.” The shortest length cladogram produced is consistent with the inclusion of the Homalonotidae in the Calymenina, and inclusion of the Calymenina in the order Phacopida. “Cheirurina” is the paraphyletic “stem group” of Phacopina. The hypothesis that Lonchocephalidae is most closely related to part of post-Cambrian Phacopida is poorly supported by protaspid characters.

The Ordovician diploporid Aristocystites Barrande lived recumbently on the seafloor but never evolved marginal frame plates or flexible tesselated surfaces. Flume studies on 1:1 scale models clearly indicate that this genus lived attached by an aboral holdfast with the aboral end of the theca facing into the current. The oral end, with its paired brachioles, fed in vortices generated in the lee of the theca. Optical current velocities for feeding probably ranged from 6 to 18 cm/sec. Growth of thecal plates and diplopore structures originated in galleried stereom. Secondary thickening occurred by growth of labyrinthine stereom. Aristocystites probably pressurized its gut as is suggested by the massive anal pyramid. Peristaltic waves through the gut would have enhanced body-fluid circulation and circulation through the diplopores. Aristocystites shows no signs of simplification in the ambulacral area. The transversely oriented, bilateral, ambulacral system is considered to be primitive. Other species synonymized with Aristocystites bohemicus Barrande from the Caradocian Zahořany Beds of Bohemia are A. desideratus, A. grandisculum, A. idealis, and A. rudis. Aristocystites metroi Parsley and Prokop, n. sp., is described from the upper Zahořany shale facies and the Bohdalec Formation from the Prague area.

Sciadiocrinus Moore and Plummer is synonymized with Schistocrinus Moore and Plummer, with the name Sciadiocrinus retained by the Law of Priority. This synonymy is based on a reexamination of the type material, study of a previously undescribed ontogenetic sequence in S. tegillum Strimple and Moore, and close inspection of separate radial plates and anal-sac spines. The holotype specimen of the type species of Sciadiocrinus was incorrectly illustrated in the original description of the genus, and appears to be immature. The basal plates of this specimen are shown to be separated from each other by the junction of the radial plates with the infrabasals—a principal character in the original concept of Schistocrinus. The Sciadiocrinus tegillum hypodigm now includes specimens which also have relatively large radial–infrabasal sutures as well as individuals with little or no contact between these plates. Examination of this collection and previously described material shows that mode of arm branching, details of radial-plate articular facets, and some features of the anal-sac spines are also equivalent in the two genera.

Sciadiocrinus, presently classified in the family Pirasocrinidae, is distinct from all known pirasocrinid taxa in a number of morphological characters. We believe the genus should be removed from the Pirasocrinidae, and recommend its assignment to the family Anobasicrinidae based primarily on similarities in arm structure. The remarkable convergence between Sciadiocrinus and the Pirasocrinidae emphasizes the adaptive significance of the spinose, umbrella-like anal-sac roof, which apparently served as a deterrent to predators.

The dorsal cups of 17 calceocrinid species illustrate the relations between ontogeny and phylogeny for this unique family. Paedomorphosis in conjunction with increasing adult body size comprises the dominant pattern. During evolution, the plate structure of the dorsal cup was rearranged so that the hinge of advanced crinoids resembles the juvenile configuration of more primitive species. Consideration of allometric equations dealing with the size and shape of the dorsal cup and hinge suggests that most changes were caused by displacements of the initial intercepts and offsets of timing in development. The growth of the hinge moment of typical taxa produces hinges that are functionally equivalent in adult crinoids of different body sizes.

Representatives of 12 conodont species, including Oulodus equirectus n. sp., have been recovered from the Silurian Lilley Formation, Lilley–Peebles transition unit, and Peebles Dolomite at six localities in southern Ohio. The Lilley, Lilley–Peebles transition unit, and Peebles belong in the Kockelella ranuliformis–K. amsdeni to Ozarkodina? crassa Chronozone and are late early to middle Wenlockian in age.

The Lilley is conformable and transitional with the underlying Bisher Formation and overlying Peebles. The unconformity between the upper Niagaran Peebles and overlying lower Salinan Greenfield Dolomite represents middle Wenlockian to late Ludlovian or early Pridolian time.

The Lilley, Lilley–Peebles transition unit, and Peebles were deposited in a gradually shoaling sea that was controlled by eustatic sea-level fall during the late early to middle Wenlockian. Uplift along the Cincinnati Arch, probably due to northward tilting of the arch, began during/after deposition of the Peebles in the middle Wenlockian. The combined effects of uplift and eustatic sea-level fall caused the sea to withdraw from southern Ohio. The Peebles was exposed and eroded prior to return of the sea to begin Greenfield deposition in the late Ludlovian or Pridolian (Ozarkodina remscheidensis Chronozone).