Larval forms of the middle and late Pennsylvanian trilobite Ditomopyge scitula (Meek and Worthen, 1865) have been collected from seven localities in the Desmoinesian of Oklahoma, Missourian of Oklahoma and Texas, and Virgilian of Nebraska and Texas. These larval trilobites have been interpreted as degree 1 through degree 8 meraspides. Although these larval forms are extremely rare, an essentially complete growth sequence was reconstructed and an ontogeny synthesized. During growth, D. scitula absorbed the brim and posterior spines into the pygidium and developed first the lateral then the median preoccipital glabellar lobes; the anterior cephalic margin is more prominent in juvenile stages, becoming narrower in late mersapide molts and finally overlapped by the glabella in early holaspide stages.

Diverse bivalve faunules in the Upper Mississippian (Chesterian) Bluestone and Hinton Formations in southern West Virginia and southwestern Virginia contain 49 species representing 29 genera. Of these, six new species are proposed: Ptychopteria pusilla, Streblochondria mutata, Streblopteria girtyi, Ectogrammysia inaffecta, E. prolata, and Cardiomorpha obovata. The Hinton and Bluestone Formations fall into Mamet's Foraminiferal Zones 18 and 19, respectively.

An assemblage of 343 species of cryptic, shelled molluscs was identified in three large samples from shallow subtidal and intertidal shelter habitats under rubble and corals at Malololailai Fiji in 1983, 1984, and 1985. One species was a polyplacophoran, 273 were gastropods (38 families), and 69 were bivalves (21 families). Cryptic gastropods were more abundant than bivalves, but showed a reduction in abundance relative to bivalves from 1983 to 1985. The abundances of many cryptic molluscs show dramatic adjustments from 1983 to 1985, chiefly due to hurricanes in 1983 and 1985, showing a decrease in equitability with increased physical disturbance. The abundance and diversity of molluscan predators in the crypts means that predation in these habitats may be substantial.

The gastropod sample diversity showed the greatest change during the 1984 post-hurricane recovery period. The 1985 hurricanes affected the sample diversity by shifting the gastropod diversity closer to what it was after the 1983 hurricane. The bivalves underwent a similar shift in sample diversity, although larger numbers of individuals in proportionately more species survived the hurricanes.

The cryptic bivalves exploited space in new crypts, while maintaining their rate of increase in abundance in the recovery period after the 1983 hurricane and through the two hurricanes in 1985. The gastropods declined in abundance after the 1983 hurricane. They recovered after the 1985 hurricanes by doubling their abundance, showing that they could exploit new resources in crypts. This increase in the gastropod population was not proportional to the increase in available cryptic space. This may mean they were still recovering in August 1985, or they may have been unable to capture their portion of cryptic space in competition with other organisms during recovery.

The 1985 hurricanes did not have much effect on the overall molluscan diversity, a possible result of pruning by the 1983 hurricane of molluscs unable to survive storms. Because there was only a short interval between the hurricanes, many molluscs that survived the 1983 event were still in the population, so that the cryptic molluscs probably were better able to deal with the effects of the 1985 hurricanes than they would have been before the 1983 hurricane. The result was that the sample diversity after the 1983 hurricane increased during the recovery period but did not decline later even though the population was devastated by hurricanes in 1985. This lends support to intermediate disturbance models linking increasing or stable diversity with disturbances spaced at intervals allowing recovery.

The euomphalacean gastropod Lytospira gerulus n. sp. is described from the Middle Ordovician of west-central Alaska. The species is among the oldest known carrier shell specimens, and also shows evidence of repaired shell breakage; the breakage may have been the result of unsuccessful predation attempts. The interior of the shell shows an unusual spiral groove and ridges that may have been associated with the animal's retractor muscle. This internal groove may be an overlooked feature of all species of Lytospira.

The middle Campanian Wolfe City Sand in northeastern Texas yields a distinctive ammonite and inoceramid fauna with Patagiosites sp., Placenticeras sp., Hoplitoplacenticeras (Hoplitoplacenticeras) minor n. sp., Baculites mclearni Landes, 1940, Trachyscaphites spiniger (Schlüter, 1872) porchi (Adkins, 1929), Inoceramus (Cordiceramus) azerbaidjanensis Aliev, 1939, and I. (Endocostea) balticus Boehm, 1907. The last-named four species allow a direct correlation with the Baculites mclearni zone of the Western Interior of the United States. The base of this zone has been dated at 79.9 ± 3.2/79.2 ± 1.6 Ma on the basis of K/Ar determinations on biotite from a bentonite. Inoceramus azerbaidjanensis is also known from the Campanian of the U.S.S.R. in Azerbaidjan (where the species was first described), western Turkemenia, Georgia, the northern Caucasus, the Crimea, and Donbass.

A diverse fauna of ostracodes comprising 21 species representing 20 genera are described from the Maxville Limestone in central Ohio. Eight new species are proposed—Roundyella incompta, Deloia spinula, Lokius morsei, Bairdia prolixa, Acratia prolata, Waylandella depresssa, Pseudobythocypris securis, and Paracavellina cooperi.

Oliganisus secunda (Croneis and Bristol), Glyptopleura costata (McCoy), and Geffenina praelonga Cooper are represented by tecnomorphs and heteromorphs. Specimens of Sansabella bradfieldi Coryell and Sohn show reversal of valve overlap.

The ostracode fauna indicates a Chesterian age for the Maxville Limestone.

Four previously undescribed arthropod trackways from the Lower Permian De Chelly Sandstone of northeastern Arizona are assigned to Paleohelcura and Octopodichnus, originally described from the Coconino Sandstone (Lower Permian) of northeastern Arizona. In addition to P. dunbari and O. minor, a new ichnospecies, O. raymondi, is described. Analysis of the De Chelly specimens, and comparison with similar tracks from the Coconino Sandstone and with experimental traces produced by modern arthropods, clarifies some problems in arthropod trace fossil analysis. The experiments support earlier hypotheses that spiders and scorpions were possible trail makers for the Coconino and De Chelly trackways, and show that features of these tracks can be used to determine direction of movement. These experiments also reaffirm that an animal can produce more than one morphology in a single trackway, patterns that would be classified as two distinct ichnogenera. In addition, the results of this research suggest that the tracks were made on slightly damp sand, and were preserved by being rapidly covered with dry sand.

Cretaceous and early Tertiary Pholadidae (Mollusca: Bivalvia) from the Pacific Slope of North America are rare and only poorly known. Three new species, each the earliest known Pacific Slope representative of its respective genus, are described: Barnea (Anchomasa) saulae n. sp. (Pholadinae) from the Upper Cretaceous (Coniacian and Santonian) Redding Formation near Redding, uppermost Sacramento Valley, Shasta County, northern California; Chaceia fulcherae n. sp. (Martesiinae) from three widely separated areas of outcrop represented by 1) the middle Miocene (“Temblor”) Temblor Formation near Oil City and in Jasper Canyon, western Fresno County, central California, 2) the middle Miocene (“Temblor”) Topanga(?) Group in the northern Santa Ana Mountains, Orange County, southern California, and 3) the upper Miocene (Wishkahan) Montesano Formation on the Middle Fork of the Satsop River, Mason County, western Washington; and Netastoma squiresi n. sp. (Jouannetiinae) from the lowest Eocene (uppermost “Meganos”) part of the Santa Susana Formation north of Simi Valley in the Santa Susana Mountains, Ventura County, southern California.

A high-spired septate gastropod, Fletcherviewia septata n. gen. and sp., occurs in a distinctive faunule at the base of the Middle Devonian Fanning River Group, within the Burdekin Subprovince, near Townsville, North Queensland, Australia. This species is one of four large, thick-shelled gastropods associated with sandstone and sandstone–limestone facies; the sediments are interpreted as shallow marine, nearshore, mobile sand bars on a moderate-energy carbonate–clastic shelf. Strategies for the algalgrazing snails on the turbulent substrate are rolling for compact robust forms and anchoring, using the wide carina, for forms such as Fletcherviewia. Septation in Fletcherviewia is rationalized in terms of the ability to vacate early whorls, thus reducing body volume and avoiding any detrimental effect as a result of loss of early-formed whorls.

Ammonites are abundant in the phosphatic base of the Annona Chalk (Campanian) near Yancy in Hempstead County, Arkansas. The following are described: Pachydiscus (Pachydiscus) sp. (very rare), Placenticeras sp. (very rare), Nostoceras (Nostoceras) pulcher n. sp. (rare), N. (N.) monotuberculatum n. sp. (scarce), N. (N.) plerucostatum n. sp. (frequent), N. (N.) danei (frequent), Didymoceras sp. (rare), Didymoceratoides binodosum n. gen. and sp. (frequent), D. clardyi n. gen. and sp. (rare), Baculites taylorensis Adkins, 1929 (abundant), B. crickmayi Williams, 1930 (common), and Baculites sp. (abundant). The diverse Nostoceras association is typical of Gulf Coast upper Campanian rocks but Didymoceratoides is a Western Interior upper middle Campanian genus. Nostoceras (N.) monotuberculatum n. sp., however, is known from a single specimen from the basal upper Campanian Didymoceras stevensoni zone in Colorado.

A new genus and species of Unionoidea, Tacuaremboia caorsii, are described from the Tacuarembó Formation (Upper Triassic–Upper Jurassic) of Uruguay. The genus is distinguished from other Unionoidea by its large size, thickness, edentulous hingeline, and the presence of claustra. It has some similarities with the Anodontinae and the Archanodontacea, but it cannot be assigned to any of the known family units.

Pegaster stichos n. gen. and sp., from the Cretaceous Chico Formation of Northern California, is the first-known fossil representative of the hitherto monogeneric Neomorphasterinae (Asteroidea: Asteriidae). Pegaster is morphologically similar to living Neomorphaster, again demonstrating the conservative evolution noted elsewhere among asteroids. Pegaster probably lived in a shallow shelf environment subject to strong storm action whereas Neomorphaster is known only from considerably greater depths; Pegaster provides a new example of an asteroid taxon excluded from shallower habitats through time.

Four new venerid species from the Cretaceous of the North American Pacific Slope are described and four previously described species are reassigned. Of the new species, two are allotted to new genera: Rhaiphiale based upon Rhaiphiale pharota n. sp. and Egrona based upon Egrona fallax n. sp., both Turonian in age and from southern California. The other new species are Loxo quintense n. sp., of late Maastrichtian age from California, and Paraesa cedrina n. sp., late Albian in age from Baja California, Mexico. The previously described species “Meretrix” arata Gabb, 1864, Turonian, and “?Meretrix” fragilis Gabb, 1869, late Maastrichtian, are placed in the new genus Callistalox; “Meretrix” lens (Gabb, 1864), Campanian age, and Flaventia zeta Popenoe, 1937, Turonian, are provisionally assigned to Paraesa Casey, 1952. This is the first identification of Paraesa from the Pacific Slope of North America. No species of Flaventia Jukes-Brown, 1908, is now known in Pacific Slope faunas.

The crustacean coprolite Favreina prima n. sp. and its internal structure are described from an upper Frasnian–lowermost Famennian limestone clast of moderately deep water origin, which derived from an Upper Carboniferous conglomerate of the Rif Mountains, northern Morocco. The fecal pellets were produced by early decapods that may be related to the Palaeopalaemonidae. Foraminifers of the stratigraphic marker genus Eonodosaria are associated with the coprolite. This is the third report of Paleozoic crustacean coprolites and the first occurrence prior to the Lower Permian.

The oldest representative of the family Palaeozygopleuridae (Loxonematoidea, Gastropoda), Palaeozygopleura chlupaci n. sp., from the Lower Devonian (Lochkovian, Monograptus uniformis Zone) of Bohemia is described. Also, its higher taxonomic position and the relationship of the families Loxonematidae and Palaeozygopleuridae are discussed. The diagnoses of both families give no unambiguous criteria for their distinction and their revision is necessary. The gradual disappearance of the deep, asymmetrical sinus in the apertural lip during the phylogeny of loxonematoidean gastropods could probably occur by two different modes and it could be produced by other changes in the mantle cavity rather than by progressive loss of the right-hand ctenidium. The family Palaeozygopleuridae is considered to be polyphyletic and, thus, is an artificial group.

The Saratoga Chalk of Arkansas yields a rich ammonite fauna of 17 species, referred to the Nostoceras (N.) hyatti zone. Recognition that the northwest European N. (N.) pozaryskii Blaszkiewicz, 1980, is a synonym of N. (N.) hyatti Stephenson, 1941, and N. (N.) helicinum (Shumard, 1861) dates the zone as latest Campanian on the basis of co-occurrence with Belemnitella langei Jeletzky, 1948, in Poland. Most previous estimates of the Campanian–Maastrichtian boundary in the Gulf Coast have been drawn at too low a level, at least in terms of ammonite faunas. Elements of the N. (N.) hyatti zone fauna occur in the United States Western Interior, and show the base of the Maastrichtian there to lie above the Baculites jenseni zone.

The Early Cambrian helicoplacoid echinoderms occur in the Cordilleran Geosyncline of western North America in strata correlated with the Atdabanian Stage of Siberia. Several higher taxa are recognized on the basis of inferred differences in the water vascular system, test organization, and external morphology. These are subclass Polyplacida Durham, with genus Polyplacus Durham; subclass Helicoplacida Durham and Caster, with n. family Helicoplacidae, type genus Helicoplacus Durham and Caster (with tubefeet emerging between two contemporaneous ambulacral plates); n. family Westgardellidae, with type n. genus Westgardella, type species H. curtisi (Durham and Caster) (with tubefeet emerging between two sequential ambulacral plates). The genus Waucobella Durham is also referred to Westgardellidae. Helicoplacus gilberti Durham and Caster, H. everndeni Durham, H. casteri n. sp., H. guthi n. sp., H. sp. a, and H. sp. b are assigned to Helicoplacidae. The genus Westgardella includes H. firbyi Durham, 1967, and W. blancoensis n. sp., in addition to the type species. No evidence of flooring plates separating the radial water vessel from the interior of the test is recognized. The mouth is at the top of the test in the interpretation adopted herein and not lateral as inferred by others; therefore, the ambulacral system is not triradiate. Illustration identified as Helicoplacus curtisi by Paul and Smith includes misidentified plates and should not be referred to this species.

On the basis of recent collections from the Upper Eocene La Meseta Formation of Seymour Island, Antarctic Peninsula, the morphology, systematic position, taphonomy, and paleoecology of the isocrinid Metacrinus fossilis are investigated. A new species, Notocrinus rasmusseni, is described as the first comatulid crinoid known from the Antarctic fossil record. The systematic assignment of M. fossilis is maintained. Basal abrasion of calyxes and absence of long attached columns suggest that M. fossilis might have lost most of the column in adult stages and lived directly on the substratum, supported by some arms and a few cirri, similar to comatulids. About 10 percent of M. fossilis individuals show brachial regeneration, in contrast to regeneration frequencies of 70–90 percent among modern Japanese isocrinids. The anomalous occurrence of isocrinids in shallow-water facies of the La Meseta is attributed to a combination of reduced predation pressure, the presumed stalkless mode of life, and a favorable temperature regime in Antarctic surface waters prior to the onset of cooling at the close of the Eocene.

Actinocamax cobbani, a new belemnitellid species from the middle Coniacian of Montana and Wyoming, is described, including univariate and bivariate biometric analyses. The species is stout and medium sized, lanceolate or strongly lanceolate in ventral view, and has adorally a low cone-shaped alveolar fracture. It may be granulated. It is compared to species of Actinocamax Miller and Gonioteuthis Bayle from the North American and North European paleobiogeographic provinces. The importance of various morphological characters, such as the shape of the guard and the structure of the adoral end, are discussed. The majority of the belemnitellids of the North American Province are endemic and the stratigraphic distribution is punctuated during the Late Cretaceous, suggesting short-lived migrations of populations from the North European Province.

The aquatic molluscan fauna of the late Oligocene–early Miocene Cabbage Patch beds of western Montana includes eight taxa, six of which are new at specific or subspecific level, Sphaerium bakeri, Valvata paula, Planorbula powelli, Biomphalaria haydeni, Lymnaea tumere, and Lymnaea vetusta ambigua. Two are referred to previously known taxa, Viviparus nanus and Lymnaea shumardi. The genera Biomphalaria, Planorbula, and Viviparus no longer occur in western Montana, nor in the Columbia River drainage. Planorbula powelli is the earliest unequivocal Planorbula from North America. Of the 18 supraspecific taxa of this molluscan fauna, eight (44%) are now displaced, all but one to the east and/or south. Climatic interpretations derived from modern habitats of the genera Biomphalaria and Polygyroidea suggest a late Oligocene–early Miocene Mean Annual Temperature of 10°C, with January means not less than 5°C, and July means about 15°C. Environmental analysis suggests a subhumid to subarid shrub and grassland vegetation similar to modern environments with > 50 cm Mean Annual Precipitation, surrounding marshy shallow lakes subject to seasonal desiccation. Effective moisture varied from slightly greater than the present for the late Oligocene to a latest Oligocene pluvial interval followed by subarid conditions for the early Miocene. Geographically, the drainage of this area was into a closed and isolated basin during the late Oligocene–early Miocene. Molluscan assemblages are found to support the tripartite division of the Cabbage Patch beds that has been based on mammals and should be useful in correlation between basins.