The emended descriptions of the genus Amphitriscoelus and the species A. waringi Harris and Hodson are given, and a new species is proposed (A. pluriloculata). These rudist bivalves are derived from a thick Lower Cretaceous sequence of carbonate sediments interlayered with siliciclastic, volcaniclastic, and volcanic rocks in southwestern Mexico, near Huetamo, in the State of Michoacan. The species belong to a recently discovered rich fauna containing other rudists, nerineid gastropods, orbitolinid foraminifers, and calcareous algae. The fauna shows a close affinity with the Amphitriscoelus fauna of northern South America. Similar assemblages are also present in Texas, Cuba and other Mexican localities. The wide distribution of the fauna allows interpretation of paleogeographic relations among all the regions as well as interpretation of paleoecological similarities. The existence of an homogeneous large faunistic province during the Early Cretaceous is suggested.

Iheringinucula, a new Tertiary genus of the family Nuculidae, is proposed. This taxon is known only from the Patagonian region (Argentina), and its range is from the late Eocene to the early Miocene. Two species are known: Iheringinucula tricesima (Ihering) from the Monte León Formation (upper Oligocene-lower Miocene) and Iheringinucula crassirugata new species from the San Julián Formation (upper Eocene-lower Oligocene?) and the Monte León Formation.

Cyphaspis wessmani new species is a morphologically aberrant taxon from the Ludlow Henryhouse Formation of south-central Oklahoma. Its long, scoop-shaped cephalic border is without close comparison in the family Aulacopleuridae, but its possession of eleven thoracic segments with an axial spine on the sixth, an inflated glabella with tiny L1 and dorsal tuberculate sculpture, a prominently expressed bilobate eye socle, and a micropygous pygidium all support assignment to Cyphaspis. The genus is common in Silurian rocks from most parts of the world, but C. wessmani is the first published record from southern Laurentia.

The description of a specimen of Aturia coxi from the uppermost Miocene of central Japan provides additional data on this poorly known Neogene species. Aturia coxi Miller is the youngest representative of this nautiloid genus, which is known from the middle to upper Miocene formations of the Indo-Western Pacific and became extinct at the end of Miocene. In addition to the presence of Aturia coxi, the abundance of tropical and subtropical benthic molluscs indicates that tropical molluscan faunas invaded mid-latitude waters around Japan in the latest Miocene. The extinction of Aturia and other Miocene molluscan genera marks the end of the Miocene Epoch.

Crassadoma monroensis new species (Mollusca: Bivalvia: Pectinidae), from the lower upper Pliocene Ochopee Limestone Member of the Tamiami Formation of southern Florida, is the first undoubted member of the genus Crassadoma Bernard, 1986, to be discovered in the Neogene on the eastern side of the Americas. The new species was likely byssate, not cemented, and fills the geographic gap between ancestral members of the tribe Crassadomini in the eastern Atlantic and Crassadoma gigantea, the giant cemented species that lives along the western shores of North America.

An anomalous pair of small, isolated calcareous sandstone bodies in the middle member of the upper Eocene Wagonwheel Formation, Wagonwheel Mountain, of the San Joaquin Valley, California, contain numerous articulated specimens of soft-bottom-dwelling bivalves. The lucinid bivalve Epilucina washingtoniana (Clark, 1925) dominates the fauna, which also sparingly contains the thyasirid bivalve Conchocele bisecta (Conrad, 1849) and the vesicomyid bivalve Vesicomya (Vesicomya) aff. V. (V.) tschudi Olsson, 1931.

The fossils in the pair of calcareous sandstone bodies, which are surrounded by deep-water silty mudstone barren of megafossils, most likely represent cold-seep communities in the upper bathyal environment. These cold seeps apparently were formed by diffusive flow through coarse sand-fill material in submarine channels.

Epilucina washingtoniana was previously known only from upper Eocene rocks on the Olympic Peninsula, Washington, and in Santa Barbara County, southern California. This species, along with a late Eocene species from Colombia, South America, are the earliest representatives of Epilucina. The Wagonwheel Formation contains one of the earliest records of Conchocele bisecta, which is a widespread Cenozoic fossil and is extant in the north Pacific. The species of Vesicomya in the Wagonwheel Formation is the earliest record of Vesicomya s.s. and has close affinity to Vescicomya (Vesicomya) tschudi Olsson, 1931, from the upper Oligocene of northwestern Peru, South America. As in the case of Conchocele bisecta, Vesicomya s.s. has not been reported previously from the Eocene of California.

The Anacacho Limestone was deposited during the Campanian and represents two depositional intervals, one of early Campanian and one of middle Campanian age. These two intervals correspond to periods of major eustatic sea level rise. This study focuses on the molluscan paleontology of the middle Campanian interval in the eastern part of the Anacacho exposure belt in Medina County, Texas. Molluscan assemblages in this area are indicative of inner to mid-shelf environments. No significant reef components are present. These eastern Anacacho deposits are interpreted to represent more offshore, deeper water environments than those to the southwest, where reef and lagoonal deposits have been reported.

Analysis of the macrofossil components from these eastern localities has expanded the number of invertebrate species known from the Anacacho Limestone by nearly three-fold. This increase in diversity, based on a small amount of new work, suggests that many more taxa are yet to be identified, particularly in the western part of the exposure belt in Uvalde and Kinney Counties. This paper documents the bivalve and gastropod fauna, discussing and illustrating 24 bivalve taxa and 11 gastropod species. Two new bivalve species are named, Panopea anacachoensis new species and Spondylus siccus new species, and two potentially new gastropod species are identified but not named herein due to inadequate material. This paper expands the distribution of many eastern Gulf Coast and Atlantic Coast taxa westward into Texas and shows strong ties between the Anacacho fauna and that of the Campanian Tar Heel and Bladen Formations of the Black Creek Group in North Carolina. The taxonomic ties between these two areas probably reflect the thorough documentation of the North Carolina fauna, which is the best documented Campanian bivalve fauna in the Gulf or Atlantic Coast regions.

The Lower Ordovician (Ibexian) Fort Cassin Formation of New York State and Vermont consists mainly of carbonates that were deposited in a subtidal storm-influenced setting. The low diversity trilobite fauna is dominated overwhelmingly by the isoteline, Isoteloides. Eleven species representing at least nine genera are described; Acidiphorus whittingtoni is new. The bathyurine genus Goniotelina Whittington and Ross is regarded as paraphyletic and is synonymized with Acidiphorus Raymond. The presence of Isoteloides canalis (Whitfield; = I. latimarginatus Fortey), I. peri Fortey and Bathyurellus platypus Fortey indicates a correlation of the Fort Cassin with the Strigigenalis caudata Zone of the Catoche Formation of western Newfoundland.

Sections in the Basin Ranges provide stratigraphic standards for the Ordovician of the U.S., from which zones based on trilobites have been widely employed in regional correlation. This paper describes new trilobite faunas from a poorly known part of the succession, at the base of the Middle Ordovician (Whiterockian) in western Utah and eastern Nevada, and including the type Ibexian section near Ibex, Utah. The faunas are from the topmost Wahwah, and overlying Juab Limestone Formations, in strata equivalent to Zone L. Although well-preserved, none of the trilobites are silicified. All are typical of inshore carbonate, Bathyurid biofacies. The majority are new species congeneric with, but different from species from the overlying Kanosh Formation. The dominant bathyurid is the hitherto little-known Psephosthenaspis, after which the new Zone is named. A threefold subdivision of the Psephosthenaspis Zone is based on successive species of the genus. The lower two of these are probably equivalent to the Valhallan Stage, described from more offshore biofacies from Spitsbergen. Eighteen species are described, of which nine are formally named as new including: Goniotelina ensifer, Petigurus inexpectatus, Psephosthenaspis microspinosa, M. glabrior, Pseudoolenoides aspinosus, Ectenonotus progenitor, Kanoshia reticulata and Pseudomera arachnopyge. The type species of a remarkable new illaenid-like bathyurelline, Madaraspis magnifica gen. et sp. nov., is described.

The base of the Paleocene Hornerstown Formation at the Inversand pit and certain other localities in New Jersey yields a diverse phosphatised fauna of Maastrichtian age, including the ammonites Pachydsicus (Neodesmoceras) mokotibensis Collignon, 1952, Sphenodiscus lobatus (Tuomey, 1854), Baculites spp., and Eubaculites carinatus (Morton, 1834). S. lobatus is known from the older Red Bank Sand and Tinton Sand in New Jersey; the other species are known only from the basal Hornerstown. Occurrences at the Inversand pit are regarded as either reworked or remainié, although details of Cretaceous/Paleocene boundary events have been destroyed by pervasive burrowing that pipes the Hornerstown down into the underlying Navesink Formation.

The marine offshore shelf mudstones of the Early Cambrian Buen Formation at Sirius Passet, North Greenland, contain a rich Konservat-Lagerstätte which includes abundant well-preserved material of the bivalved arthropod Isoxys volucris new species. The new material confirms Isoxys Walcott, 1890 as a component of the earliest arthropod faunas worldwide. Isoxys species are known from the Early Cambrian of Spain, Siberia, South Australia and Southwest China and also from the Early to Middle Cambrian of Laurentian North America. Isoxys occurs in the Redlichiid, Bigotinid and Olenellid trilobite faunal realms but is restricted to within tropical/subtropical regions, attesting to possible paleolatitudinal controls on its distribution. Isoxys resembles some phyllocarid and bradoriid arthropods but without knowledge of its soft-parts the affinity of the genus remains uncertain.

A distinctive new genus (Xyoeax) and two new species (Xyoeax eponcus, Scutellum sudorum) of styginid trilobites are described from the late Early Devonian (Emsian) Murrindal Limestone of eastern Victoria, Australia. Limited material of a third styginid species not belonging to any named genus is also described from the same locality. Xyoeax is considered to be closely related to Ancyropyge Clarke, 1891, and Weberopeltis Maksimova in Moore, 1959, and less closely related to Kolihapeltis Prantl and Přibyl, 1947. Weberopeltis is revised and newly diagnosed. Several species previously assigned to Weberopeltis are transferred to the new genus Exastipyx, which is considered to be related to Cornuscutellum Snajdr, 1960. Ancyropyge, Exastipyx, Weberopeltis, and Xyoeax all have pygidia with long pleural spines derived by reduction of the pleural field between the pleural ribs, whereas Kolihapeltis and Cornuscutellum lack pygidial spines. Pygidial morphology of Xyoeax type has thus arisen independently in separate styginid lineages. The type species of Altaepeltis Maksimova, 1968 is established as Weberopeltis bublitchenkoi Maksimova, 1960, by monotypy.

Four species of carabocrinids from the Ordovician of northern Iowa and southern Minnesota are described, namely Carabocrinus radiatus E. Billings, C. vancortlandti E. Billings, C. magnificus Sardeson from the Middle Ordovician Dunleith Formation and C. slocomi Foerste from the Upper Ordovician Maquoketa Formation. Carabocrinus radiatus and C. vancortlandti are also known from the Middle Ordovician of Ontario and Quebec. In addition, C. magnificus and C. vancortlandti are recorded from the Decorah of the Twin Cities area and the Curdsville Limestone of Kentucky, respectively. Biogeographically, the Middle Ordovician carabocrinids from Iowa and Minnesota are most similar to those from rocks of similar age in the northern Appalachians.

Development of the cup and its component plates in C. slocomi is almost entirely isometric so that the its shape is largely constant regardless of size. This species exhibits ridge canals on the shoulders of the radial plates in the cup. The ridge canals probably served for respiration. As expected, the number of ridge canals and their length increase with positive allometry compared to the size and volume of the cup. Growth of the ridge canals restricts the width of the radial facets.

At the southernmost tip of South America, a thick pile of deep marine volcaniclastic rocks called the Yahgan Formation (Kranck, 1932) was deposited during the Early Cretaceous in a small marginal basin developed between the continent and a Pacific-facing volcanic arc (Katz, 1972; Dalziel et al., 1974). North and northwest of Tierra del Fuego, in the adjacent Austral or Magallanes basin, this unit is laterally replaced by coeval, fine-grained deposits representing basinal, slope, and platform marine settings (Winslow, 1982; Biddle et al., 1986; Wilson, 1991). The geometry of the basins changed markedly with a compressional event that produced the tectonic inversion of the marginal basin and the formation of a retroarc foreland basin in front of the rising cordillera. Closure of the marginal basin and strong deformation of the Yahgan Formation apparently occurred in the mid-Cretaceous (Halpern and Rex, 1972; Dalziel et al., 1974; Wilson, 1991); however, the timing of the opening and closing of the basin is poorly constrained because of the scarcity of fossil evidence. So far, a Late Jurassic-Neocomian age was favored for the Yahgan Formation on the basis of the record of belemnites and ammonites (Aguirre Urreta and Suárez, 1985; Halpern and Rex, 1972; Winn, 1978). Halpern and Rex (1972) mentioned the Hauterivian genus Favrella in Gardiner Island, but this record has been questioned by Thomson et al. (1982) who considered the ammonite imprint to be some kind of heteromorph. Also, the timing of the transition from marginal to foreland basin is not well documented. On the basis of indirect evidence the initiation of the foreland basin stage was assigned to the Albian in the Ultima Esperanza region of Chile (Wilson, 1991) and to the Late Cretaceous in northern Tierra del Fuego (Biddle et al., 1986). Recent field work by the authors in the area of No Top Mountain-Moat River, Tierra del Fuego (Figure 1), has resulted in the first record of diagnostic late Albian inoceramids in the Yahgan Formation. The objective of this note is to document this fauna and to briefly discuss its implications on the control of the timing of the transition from marginal to foreland basin in the area.

Phosphatized, three-dimensional cuticle fragments of the palaeoscolecids Houscolex lepidotus new genus and new species, Houscolex species indeterminate, and an unidentified form are described from the Lower Cambrian Qiongzhusi Formation of Shaanxi, China. These segmented worms, characterized by regularly arranged simple plates and platelets, small circular pores and fine pits, and irregularly distributed nipplelike protuberances, are unique among known palaeoscolecids. The occurrence of such cuticles as seemingly persistent elements of phosphatized faunas suggests that wormlike organisms achieved a fairly high diversity and widespread geographic distribution during the Early and Middle Cambrian.

The extant irregular echinoids Echinoneus cyclostomus Leske and Brissus unicolor (Leske) are reported from the middle Pleistocene of Barbados. The moderately robust E. cyclostomus is well-preserved, while B. unicolor, which had a thin test in life, occurs as an internal mold. The holectypoid E. cyclostomus sensu lato occurs in fossiliferous deposits of Upper Oligocene to Pleistocene age in the Antillean region, showing remarkably little overall variation in test shape during this period. Similarly, gross morphological features of Recent B. unicolor are not dissimilar to those seen in some Caribbean species from the Paleogene, such as B. sp. cf. B. unicolor from the Middle Eocene of Jamaica. Superior fossil specimens will be required to determine if certain fossil species within these genera are valid. This analysis supports the observation that many taxa of the modern Antillean, shallow-water echinoid fauna have essentially persisted within the region since at least the Oligocene.

Shelf-derived limestone boulders in debris flows of the Cow Head Group, western Newfoundland, have yielded rich mid- to Upper Cambrian trilobite faunas. The agnostoid component of Marjuman boulders consists of 23 species assigned to 11 genera; Kormagnostus boltoni and Kormagnostus? copelandi are new. Cladistic parsimony analysis of the Ptychagnostidae Kobayashi reduces this family to 3 genera: Ptychagnostus Jaekel, Pseudophalacroma Pokrovskaya and Lejopyge Hawle and Corda; Ptychagnostus includes three non-obligate subgenera: P. (Ptychagnostus) (= Tomagnostus Howell); P. (Goniagnostus) Howell and P. (Aotagnostus) öpik (= Myrmecomimus öpik). Correlation with zonations established in northern Canada and Utah indicates that the Cow Head Group includes a nearly complete sequence of agnostoid faunas from the mid-Cambrian Ptychagnostus gibbus Zone to the Upper Marjuman Cedaria brevifrons Zone.

The genus Cyphaspis Burmeister, 1843, is first known from the northern Laurentian Sheinwoodian. By the late Homerian, the genus had appeared in England and Baltica, and from the Ludlow through the Lower and Middle Devonian it had an essentially cosmopolitan distribution. The Mississippian Dixiphopyge Brezinski, 1988, may represent a relict distribution of Cyphaspis, and if so should be considered a junior subjective synonym. Cyphaspis is considered the sister taxon of Otarion Zenker, 1833. The oldest, Sheinwoodian, species of either genus are very similar, but the clades evolved to the point of gross morphological disparity in the Devonian.

New species from the Wenlock and probably Ludlow of northwestern Canada are Cyphaspis lowei, C. munii, C. buchbergeri, and C. mactavishi. New ontogenetic material of the Zlichovian C. dabrowni (Chatterton, 1971) further demonstrates the pervasiveness of the basic juvenile morphology of the tribe Otarionini.

A model for crinoid plate circlet homologies is proposed based on a tricyclic (four-circlet) aboral cup, with Aethocrinus the characteristic tricyclic crinoid. The plate circlets in the aboral cup of Aethocrinus, from bottom to top, are lintels (named herein), infrabasals, basals, and radials. In this model, traditional interpretation is maintained for the aboral cup plates of most crinoids. Cladids, flexibles, articulates (primitively), and diplobathrid camerates are dicyclic and are composed of infrabasal, basal, and radial circlets. Monobathrid camerates are monocyclic, and they have basal and radial circlets. Disparid plate circlet homologies are reinterpreted. Among disparids, “basals” are lintels, “inferradials” and “radials” are infrabasals, and “superradials” are radials.

The “Law of Wachsmuth and Springer” is judged to be a relationship that has most fidelity applied to lumen angles. This “law” is considered to be only a consequence of development and not an invariable basis by which to determine plate homologies. In the model presented here, plates cannot be shifted around after the juvenile calyx is sutured, and arms may grow on either radials or infrabasals, whichever plates are at the top of the cup when arms begin to grow.

Glabellar lobes of holaspid cranidia of trilobites have been numerically designated, LI, L2, etc. (Jaanusson, 1956; Henningsmoen, 1957, figure 1), or lp, 2p, etc. (Harrington, 1959), forward from the occipital ring; most trilobites have four glabellar lobes and an occipital ring. The description of morphological structures with an identical term implies that the structures are homologous in different organisms of a certain group (Inglis, 1966); this is one of the classical definitions of homology (Patterson, 1982). This also seems to be an initial conjecture of homology (“primary homology” of de Pinna, 1991). Likewise, the numerical notation of glabellar lobes should allow us to recognize homology of the lobes among trilobite taxa. Under the above traditional system, the homology is demonstrably recognized in ontogenetic stages with a distinctively differentiated protopygidium (stage 2 in Figure 1); however, this is not the case for earlier intervals occurring before transverse demarcation at the back of the head (stage 1 in Figure 1). This limitation is because the relationships of the occipital ring of the later stages to the posterior axial lobes of the earlier ones are uncertain, and this can be appreciated, when describing a phacopoid protaspis with four axial lobes (stage 1 of Rossaspis pliomeris in Figure 1). We introduce a new term, “Lp”, for the posteriormost axial lobe to remove this limitation, while keeping the traditional system useful. The previous system using letters “L” (after lobus) and “S” (after sulcus), proposed by Jaanusson (1956, p. 37), is preferred over the system using “p”, because “p” of the latter confusingly refers to lobes or furrows (e.g., Harrington and Leanza, 1957, p. 221)