A new genus, Popenoeum, is proposed for a clade of Upper Cretaceous through lower Eocene pseudolivine gastropods found in North and South America, West Greenland, western Europe, and southern India. Popenoeum n. gen. is characterized by tabulate whorls with a prominent subsutural canal, collabral costae that terminate as tubercles on the body whorl shoulder, and closely spaced fine to strong spiral cords.

The type species, Popenoeum maritimus n. sp., is from the lower Paleocene (Danian) portion of the San Francisquito Formation, southern California, and from the upper Paleocene (Thanetian) Sepultura Formation, Baja California. Popenoeum maritimus bajaensis n. subsp. is also present in the Sepultura Formation.

Other species and subspecies in the clade include Popenoeum sp. (Toulmin) and P. scalina Heilprin from Alabama; P. mutabilis mutabilis (Woods) and P. mutabilis woodsi (Olsson) from northwestern Peru; P. aff. P. maritimus from West Greenland; P. brevis (Doncieux) and P. prima (Defiance) from France; P. chavani (Glibert), P. robusta (Briart and Cornet) and P. briarti (Vincent) from Belgium; and P. subcostata (Stoliczka) from southern India. The earliest species is P. subcostata, and it is the only Cretaceous species. The youngest form is P. mutabilis woodsi, and it is the only Eocene species. The new genus reached its peak during the Paleocene.

Rostroconchs are a common faunal component in the Devonian rocks of Ohio, particularly in the Columbus and Dundee Limestones. Hippocardia cunea (Conrad) is the most abundant species. Also present are H. monroica (Grabau), H. ohioense (Meek), H. curta n. sp., and Bransonia? sibleyense (La Rocque).

Growth series of Hippocardia cunea show that the large hood and the rostrum begin to develop early in ontogeny. The rates of increase in the number of comarginal growth increments on the posterior or rostral face and radial ribs on the body of the shell are slow; most size increase of the shell occurred in the increasing widths of the ribs and the interspaces. The length/height ratio increases from young to juvenile specimens and then decreases in adult specimens. However, the length/width and height/width ratios show a general decrease from young to adult specimens. Considerable variation in shell lateral profile is present in H. cunea.

Three specimens of Hippocardia cunea show borings entering the posterior rostral portion of the shell, presumably made by Trypanites, a polychaete worm. In one instance, a boring caused disfiguration of the shell material indicating that the host was alive at the time of the boring. The orientation and location of the borings and the presence of one specimen believed to be preserved in life position provides the base for interpreting H. cunea as an infaunal deposit feeder.

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, E2b–c undifferentiated. Foraminifera place the formation in Mamet zone 19. The bivalve fauna discussed herein was collected from the E2b–c portion of the Imo.

Biostratigraphic correlations of the Conasauga Formation in the southern Appalachians have been hindered by unreliable trilobite taxonomy. New fossil collections and re-examination of type specimens allow revision or confirmation of assignments for several Middle Cambrian trilobite taxa. These revisions reveal sufficient relationships with trilobites outside the region to place fossiliferous strata in Floyd County, Georgia, into the Oryctocephalus and Bolaspidella assemblage zones of the Middle Cambrian section defined for the Great Basin.

Trilobite taxa considered are: (Agnostida) Baltagnostus centerensis (Resser, 1938) and Peronopsis cf. P. cuneifera (Barrande, 1846); (Ptychopariida) Alokistocare americanum (Walcott, 1916), Elrathia antiquata (Salter, 1859), Asaphiscus gregarius Walcott, 1916, and Glyphaspis cf. G. capella (Walcott, 1916).

Two new spine-bearing gastropods, Chlupacispira spinosa n. gen. and sp. and Spinulrichospira cheeneetnukensis n. gen. and sp., are described from the late Early Devonian (Emsian) and early Middle Devonian (Eifelian), respectively, of west-central Alaska. These represent the earliest reported spiny pleurotomariacean gastropods. Otherwise, spinose pleurotomariaceans are known from strata no older than Carboniferous age. Spinulrichospira cheeneetnukensis n. gen. and sp. appears to represent a more highly ornamented derivative of Ulrichospira Donald. Both new genera are part of the more highly ornamented fauna which occurred in warm equatorial waters of the Old World Realm during the Early and Middle Devonian, in contrast to more weakly ornamented shells of the Eastern Americas Realm and even more weakly ornamented (almost totally “plain”) shells of the Malvinokaffric Realm. The latter two realms are thought to represent subtropical to warm temperate and cool temperate to cool polar conditions, respectively.

Lacertasterias elegans and Schondorfia fungosa are new genera and species of multiarmed asteroids described from the Kinderhookian? (Mississippian) Gilmore City Formation of Iowa and the Chesterian (Mississippian) Haney Formation of Illinois, respectively. Based on ambulacral construction, the former belongs to the Paleozoic asteroid stem group whereas the latter is distinct from but closer to post-Paleozoic asteroids.

The multiarmed condition is atypical today; nevertheless, multiarmed species are morphologically varied and taxonomically widely distributed. The condition is considered problematic; it is uncertain whether or not multiarmed organization is adaptively neutral. Although only convergent with rather than ancestral to post-Paleozoic multiarmed asteroids, both new genera share important similarities with modern multiarmed predators, implying a predatory life mode for the fossils. The similarity between phylogenetically disparate Paleozoic and post-Paleozoic asteroids implies the multiarmed condition is beneficial, and benefits endured in spite of the major biotic changes that occurred around the end of the Paleozoic.

The ammonite species Puzosia (Mesopuzosia) densicostata Matsumoto, Kitchinites (Neopuzosia) japonicus Spath, Anapachydiscus cf. A. nelchinensis Jones, Menuites cf. M. menu (Forbes), Submortoniceras chicoense (Trask), and Baculites cf. B. boulei Collignon are described from Santonian–Campanian strata of western Canada and northwestern United States. Stratigraphic occurrences and ranges of the species are summarized and those taxa important for correlation with other areas in the north Pacific region are noted.

A diverse, well-preserved assemblage of nautiloid cephalopods was collected from the Treptoceras duseri shale, a 1.5-m-thick claystone within the Waynesville Formation (Late Ordovician, early Richmondian) exposed in southwest Ohio. The strata, the enclosed fauna, and its taphonomy indicate deposition in a low-energy, mud-bottom marine environment, in water depths of 20–25 m, below wave base but within the zone of storm-current reworking.

Nautiloid specimens consist of complete conchs that have been replaced by calcite. Twelve species of nautiloids, belonging to eight genera, representative of four orders, have been collected from the shale in southwest Ohio. Longiconic orthocones are clearly the dominant nautiloid morphotype present, with the assemblage dominated by three species of the longiconic orthocerid Treptoceras and with fewer numbers of the endocerid Cameroceras and the slender orthocerid Isorthoceras?, the cyrtoconic oncocerids Oncoceras and Manitoulinoceras, and rare specimens of the orthocerid Gorbyoceras, the oncocerid Zittelloceras, and the ascocerid Schuchertoceras.

Nautiloid taphonomy, the diversity of nautiloid taxa present, the lack of postmortem buoyancy in the shells of the more common taxa, the recurrent nature of this assemblage, and the restricted distribution of this Treptoceras–Cameroceras fauna to portions of eastern North America in the Late Ordovician suggest that this nautiloid assemblage represents an in-situ accumulation of nautiloids representative of a living assemblage. These nautiloids were important elements associated with benthic communities in these epeiric sea mud-bottom environments and not simply assemblages of drifted, necroplanktonic shells.

Waldemaria monticola Pierce n. sp. and “Hendersonia” valida Pierce n. sp. are described from fluviatile sediments of the intermontane Flint Creek Basin of western Montana. The genus Waldemaria was previously known only from Japan. The presence of these two genera suggest a marked climatic cooling when compared with western North American Eocene–Oligocene faunas. The stratigraphy of the Flint Creek beds, and the associated vertebrate fauna, diagnostic of an early Barstovian age (17–15 Ma), is summarized.

Propeamussium (Parvamussium) holzense n. sp. and Propeamussium (Parvamussium) robinsonense n. sp. are described from the Upper Cretaceous Holz Shale Member of the Ladd Formation, Santa Ana Mountains, southern California. These species occur with Bostrychoceras elongatum (Whiteaves), Glyptoxoceras subcompressum (Forbes), and Inoceramus orientalus (Sokolow), which are indicative of a late medial Santonian age (Bostrychoceras elongatum Biochron). Propeamussium (Parvamussium) cowperi (Waring), from the Campanian Chatsworth Formation of the Simi Hills, southern California, is also redescribed and reillustrated for comparative purposes.

Thin sections and acetate peels of the sediment within, and adhering to the outsides of, tests of Late Eocene echinoids from the southeastern United States have proven to be useful checks on inferences from test morphology concerning substrate preference. Previous characterizations of species' sediment preferences have concentrated primarily on the functional morphology of spatangoids, and relied particularly heavily upon Recent relatives of nonspatangoids. Reassessment of the preferences of spatangoids has led to a few discrepancies between interpretations herein and those of previous workers. In addition, this study attempts a more thorough assessment of functional morphology of nonspatangoid irregular echinoids than has previously been tried.

Carbonate sand-dwelling species from the Ocala Limestone (thin sections are clean grainstones) include Oligopygus, Echinolampas, Rhyncholampas, fibulariids, Durhamella, Neolaganum, Agassizia, Macropneustes, some species of Plagiobrissus and Periarchus, and most species of Eupatagus. All these have been interpreted previously as preferring clean sand. Species that preferred, or at least tolerated, significant carbonate mud in the substrate (thin sections are poorly washed grainstones and packstones) include all the regular echinoids and the irregular echinoids Schizaster, Ditremaster, Brissopsis, Brissopatagus, Amblypygus, Eurhodia, Weisbordella, Wythella, Paraster, some species of Periarchus and Plagiobrissus, and perhaps some species of Eupatagus. The last seven of these have previously been interpreted as sand-dwellers.

In general, species preferring mud-rich sands are found in the upper Ocala of peninsular Florida and in the middle to upper Ocala equivalents in the rest of the Gulf Coast. Sand-dwellers are most often found in the lower Ocala strata of both regions and up into the middle Ocala in Florida. These generalizations are consistent with existing paleoenvironmental models for the region.

Isolated, uncompressed specimens of Monograptus spiralis show that the thecae become increasingly asymmetric and twisted distally and that the lateral margins of the apertures possess lobate veins and extend laterally as spatulate rostral processes. These too become increasingly asymmetric distally.

Three species of Cyrtograptus, obtained uncompressed from the same and overlying strata, are compared with M. spiralis. They show little similarity in the details of proximal or distal thecal form. Cyrtograptus sakmaricus possesses more stout, overlapping proximal thecae, while those of C. cf. C. laqueus are slender and elongate. In both species, the thecae are moderately asymmetrical, become simpler and less strongly hooked distally, and have simple lateral margins. The third species, Cyrtograptus sp., possesses proximal thecae very like those of C. sakmaricus, but its distal thecae, while strongly twisted, are very much simpler than the type found in M. spiralis.

Despite superficial rhabdosomal similarities in flattened material, the thecal details clearly indicate that M. spiralis is very unlikely to be ancestral to any known species of Cyrtograptus owing to its unique and highly specialized thecal form. Comparison among species of Cyrtograptus suggests, however, that this genus might be polyphyletic, with its ancestors being other members of the “Spirograptus” group.

The Upper Devonian–Lower Mississippian sequence in the subsurface of north-central Iowa and southeastern Nebraska consists of the Lime Creek, undifferentiated Sheffield–Maple Mill, English River, Prospect Hill, and Chapin Formations. The Lime Creek is restricted entirely to the Polygnathus biofacies where conodonts are present and correlates with an interval from Zone 4b to Faunal Interval 8 of the Canadian (Alberta) Rockies zonation based on conodonts and foraminifers. The oldest identifiable Famennian units range in age from the crepida–rhomboidea Zones at locality 1 to the Upper marginifera Zone or younger at localities 2 and 3. The youngest Devonian strata may occur in the Upper expansa Zone at locality 1 and Middle expansa Zone at localities 2 and 3. Famennian faunas are present in the Polygnathus biofacies at localities 1 and 3 and in the Icriodus biofacies at locality 2. A total of 50 species and subspecies are identified, four of which have not been previously described (Icriodus sp. A, Hemilistrona sp. A, Polygnathus depressus n. sp., and Polygnathus sp. B).

Twenty-eight specimens of well-preserved macrurous decapod crustaceans, collected from the Lopez de Bertodano and Sobral Formations on Seymour Island, Antarctic Peninsula, form the basis for description of Metanephrops jenkinsi n. sp. Based upon associated cephalopods, foraminiferans, and palynomorphs, the age of the occurrences ranges from Maastrichtian to Paleocene. The discovery extends the range of the genus from the Pliocene into the Cretaceous and extends the southern limit of the geographic extent of the genus from New Zealand to Antarctica.

Lapparia sp. A of Toulmin (1977), from the early Eocene Hatchetigbee Formation of Alabama, is referable to the Tethyan genus Volutilithes and is conspecific with Voluta clarae Harris. This is the first certain record of Volutilithes in the Paleogene of the Gulf Coastal Plain and only the third record of the genus in North America. Trans-Atlantic migration of this tropical genus to the New World apparently occurred during the early Eocene. Its northward expansion into the higher latitudes of Alabama and southern California was probably in response to early Eocene climatic warming.

In addition to Volutilithes, many other molluscs with Tethyan affinities are present in the Paloegene deposits of the Gulf Coastal Plain. These Tethyan elements, however, differ from those reported from the Eocene of peninsular Florida. The presence of a filter-bridge barrier, the Suwannee Channel, between the eastern Gulf shelf and the Floridian carbonate platform during the Paleogene may account for this difference.

Modern Nautilus, in natural and laboratory settings, scavenges both dead and molted decapod crustaceans. Ingestion of palinurid lobster exuviae by Nautilus follows a specific pattern in which the cephalopod consumes the exoskeleton beginning at the posteriormost part of the abdomen and continuing anteriorly. During the ingestion process, the cephalothorax is least likely to be consumed, either because the Nautilus may abandon the remains, or the cephalothorax may become separated from the abdomen at its weakest point, the articulation of the cephalothorax with the abdomen. Examination of 767 fossil lobster specimens from 50 formations, 41 of Cretaceous age, demonstrates that the fossil record of lobsters, the preponderance of which appear to be exuviae, is strongly biased in favor of cephalothoraxes. Observations on Nautilus suggest that anatomically selective scavenging by ancient cephalopods, both nautiloids and ammonoids, may explain, in part, the selective preservation of lobster cephalothoraxes over abdomens. Despite the range of variation in jaw morphologies among ammonoids, probably most could have fragmented and ingested decapod remains. Evidence for selective scavenging in the geologic past is purely circumstantial; no cephalopod bitemarks have been identified on fossil lobster exuviae. Pre-burial decomposition of connective tissues and subsequent disarticulation of the abdomen in the absence of scavenging may also have contributed significantly to the observed anatomical taphonomic bias.

The burrow structures of Heterocerus brunneus Melsheimer and its larvae are described from both field (northeastern Kansas) and laboratory habitats. These are further interpreted in light of known North American heterocerid biology. Two important observations are that significant features of any one burrow varied with the consistency (especially the water content) of the substrate, and that different insects were making superficially similar burrows at the same field site. It would require exceptional preservation, or associated body parts, to positively identify fossil traces of these structures as heterocerid burrows, but their general pattern should be readily recognized as foraging traces in even the most degraded preservations.

The Fossil Hill Member of the Prida Formation (Fossil Hill, Nevada) yields one of the most continuous records of Middle Triassic conodont evolution currently known. Because of different taxonomic viewpoints, this record has been alternately interpreted to represent either morphological stasis or gradual, biostratigraphically significant morphogenesis. Univariate and multivariate morphometric analysis of 18 successive Neogondolella Pa element populations suggests that the majority of specimens at Fossil Hill (including N. constricta emend. sensu Nicora and Kovacs, 1984) belong to a single, morphologically diverse species, Neogondolella mombergensis (Tatge). Time series of individual character means from 18 stratigraphic horizons in the Fossil Hill display nondirectional morphologic trends for which a random walk model cannot be rejected. Time series of transformed multivariate means constitute biologs that may prove useful in regional correlation.

Trilobites assigned to the Elvinia Zone (Lower Franconian, Upper Cambrian) have been recovered from the Collier Shale in the Ouachita Mountains of west-central Arkansas. The trilobites are preserved as disarticulated exuviae, and are found in both dark-colored limestone clasts and dark, thinly-bedded carbonate layers. Field observations and petrologic/petrographic evidence indicate that these trilobites were originally deposited in a deep-water, outer shelf setting, and that shortly after deposition they were transported by sediment gravity flows to the continental slope or basinal plain.

The faunal assemblage is very similar taxonomically and taphonomically to faunas of the Elvinia Zone previously reported from North American shelf environments. Two distinctive trilobite assemblages occur in the Collier Shale. Most common is a diverse fauna that is correlative with the middle to upper part of the Elvinia Zone in Missouri, Oklahoma, and Texas. One locality yielded numerous trilobites characteristic of the Irvingella major Subzone, which occurs at the top of the Elvinia Zone in these areas. These Elvinia Zone trilobites belong to the North American Faunal Province, a largely endemic group restricted to shelf environments around the perimeter of the North American craton. Their occurrence in the Collier Shale strongly indicates that the original site of Collier deposition was proximal to the Upper Cambrian shelf margin and that the Ouachita sedimentary section is not an exotic terrane.

More than 7,900 trilobites were identified during this study; they are assigned to 26 genera and 27 species. The family Cliffidae is proposed for a group of trilobites that includes species of Cliffia Wilson, Aphelotoxon Palmer (junior synonym Ponumia Hu), Drabia Wilson, and possibly Elyaspis Kurtz. Three new genera are erected (Kymagnostus, Pyttstrigis, and Jessievillia) and 10 new species are described and illustrated (Apachia genaitholix, Cliffia magnacilis, Dellea planafrons, Iddingsia hapsis, Jessievillia radiatus, Kymagnostus harti, Neoagnostus? dilatus, Aphelotoxon lumaleasa, Pulchricapitus fetosus, and Pyttstrigis dicilia).

Two species of the heteromorph ammonite genus Diplomoceras Hyatt are described from the Upper Cretaceous of the James Ross–Seymour Islands area, Antarctica. The late Campanian–early Maastrichtian D. lambi Spath has a relatively high rib density, whereas D. maximum n. sp. has a lower rib density and is known only from the uppermost Maastrichtian of the Lopez de Bertodano Formation on Seymour Island. Both species attain an exceptionally large size with the body chamber of D. maximum n. sp. attaining a length in excess of one meter. The structure of the shell wall in Diplomoceras is characterized by the thickening of the nacreous layer below the ribs. The shell thickening results in an inner flat surface and a smooth phragmocone. Reconstruction of the shell suggests at least four parallel shafts and three U-connectives. Estimates of the total density, center of buoyancy, and center of mass in this reconstructed shell indicate a slightly positive buoyant shell with a relatively unstable floating position.