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The common belief currently shared by many geoscientists concerning the climatic interpretation of limestones is that a warm-water environment is essential. This concept is not necessarily true because the rate and extent of terrigenous sediment dilution, rather than water temperature, is the primary factor determining whether or not a limestone forms at nearshore or continental shelf depths. Because carbonate productivity is lowest in cold climates, however, CaCO3 abundance and the thickness of carbonate accumulations tend to be least at high latitudes. In this regard present-day continental shelves and beaches offer a poor model for comparing cold-water and warm-water carbonates because of the generally emergent continental tectonic framework, recent eustatic sea-level changes, and the presence of ice caps at the modern poles. Typically, the influence of climate on non-reef continental shelf and beach environments cannot be clearly distinguished by the presence or absence of major taxonomic groups. Faunal diversity and equitability are more sensitive in this regard. The absence of shelf-depth inorganic carbonate precipitates, micrite envelopes, and peloids may also point to the cold-water origin of a rock. Skeletal mineralogy and oxygen isotopes of certain unrecrystallized carbonates may be good paleoclimatic indicators; however, trace elements and physical-textural attributes of the carbonate fraction are probably temperature insensitive. Previous studies of high-latitude continental shelves have concentrated merely on the abundance of calcareous material and there is seemingly a disproportionate amount of information with respect to low-latitude carbonate studies. Further research on cold-water carbonates may open up new avenues for alternative paleoenvironmental and paleoclimatic interpretations.

Polychaete shell-borings are widespread but not often common in Paleozoic strata of most continents, occurring in pelecypod, gastropod, cephalopod, coral, stromatoporoid, crinoid, brachiopod, ectoproct, and calcareous algal skeletons of Ordovician to Permian age. Four genera are known: Vermiforichnus (Spionidae), Ordovician to Permian; Caulostrepsis (Spionidae) , Devonian to Oligocene; Myzoslomites (Myzostomidae), Ordovician to Jurassic: and possibly Conchotrema , Devonian to Permian. The Silurian Citonia sipho is a worm-boring, not a calcareous worm tube, referable to Vermiforichnus . An exceedingly well preserved Devonian fossilized polychaete, Vermiforafacta rollhisi , with complex setigerous parapodia, dorsal cirri, peristomial cirri, prostomium, and tentacle-like palps, occurs entombed in an agglutinated tube-lined worm-boring ( Vermiforichnus ) . It may have been a shell-borer considering its many similarities to the spionid, Polydora , which apparently ecologically replaced it. Like Polydora, Vermiforafacta probably filtered food and sediment from sea water and constructed agglutinated tubes which lined its borings. In bivalves, borings parallel valves and are usually perpendicular to commissures; in massive skeletons, they radiate outward and laterally. Distorted later growth and “blisters” indicate that the host was often alive. Commensal to pathogenic parasitism existed and worms benefited from their hosts's feeding currents and protective shells. One polychaete nestler is reported. Life positions of hosts are sometimes indicated.

"Tadpole nests" are a true biogenic sedimentary structure known only from the Recent. All known occurrences of supposed fossil forms have been disputed and are considered to be interference ripple marks of inorganic rather than of organic origin. Silurian, Carboniferous, and Triassic "tadpole nest"-like structures could not have been produced by tadpoles because frogs did not appear until the Jurassic Period. A new occurrence of Recent "tadpole nests" from New York indicates that tadpoles produce nests with their tails while feeding from bottom sediments and that their delicate nature severely limits their chances of preservation in the fossil record. The term "tadpole holes" (Dionne, 1969) is unnecessary because the term it was meant to replace, "tadpole nests," is correct by definition. Although Benjaminichnus Boekschoten, 1964, was proposed for Recent "tadpole nests" and was also intended for any fossil forms that may some day be found, it is an objective synonym of Batrachiodes Hitchcock, 1858 ( non Lacepede, 1800), an inorganic sedimentary structure (interference ripple marks). We recommend strongly that Recent biogenic sedimentary structures, and other potential trace fossils with known producers, not be given formal taxonomic names. Instead, the taxonomic (or colloquial) name of the organisms responsible for a structure should be used for reference. The possibility of such a structure being found as a trace fossil is insufficient justification for giving it a taxonomic name.

The Eocene-Miocene contact in the Delaware coastal plain should be moved down and placed below the pebbly, glauconitic sand of the uppermost Piney Point Formation (Jacksonian age). The uppermost part of the Piney Point Formation (glauconitic greensand), which is pebbly, lacks a characteristic late Eocene fauna and contains middle Miocene Foraminifera, unquestionably making this pebbly sand Miocene in age. Thus, a new correlation can be drawn on the basis of the microfossils, rather than on the green color due to the presence of glauconite.

Coastal back-barrier salt-marsh environments are evaluated as possible modern analogs for some coal-forming basins. Analysis of the amount of organic matter in Holocene salt-marsh peats from 158 core samples at Plum Island, Massachusetts, indicates that the organic matter content is too low to ultimately produce coal. C-14 dates indicate depositional rates of 1 mm/yr. Both the high and low salt-marsh peat facies would probably diagenetically alter to a carbonaceous shale. A review of the organic content reported from other nondeltaic back-barrier and coastal salt-marsh environments indicates that they commonly have too much detrital material to classify as coal precursors. Barrier-island systems, being affected by sea-level changes and subject to landward migrations, also lack long-term stability needed for coal formation. These data suggest that modern back-barrier environments are not good analogs for coal-forming basins.

A number of recent studies cast doubt on the reliability of using size-frequency distributions of fossil species for inferring ecological age-survivorship curves, fossil community structure, and paleoenvironments. Survivorship curves for fossil taxa are really post-larval size-survivorship curves. Data are lacking for the normally enormous mortalities that occur during larval stages. Such curves represent the effects of differential taphonomy upon various size classes. Before dismissing the paleoecological application of ecological survivorship curving, the patterns of sizefrequency distributions of very large and spatially disparate populations of extant species should be explored. Emphasis to date has been upon temporal, not spatial, averaging in the generation of fossil assemblages. We provide size-survivorship and reconstructed age-survivorship curves on over 2.5 million live individuals of the infaunal bivalve Mya arenaria from 1, 093 collecting sites at 15 locations within four estuaries from eastern Massachusetts. A significant difference was found among the cohort structures of post-larval M. arenaria from the four estuaries, even though environmental settings were similar. A summary cohort curve was constructed that may be analogous to very extensive (but perhaps unlikely) spatial averaging in the generation of a fossil assemblage. The size-survivorship curves constructed for the four estuaries and for the 15 locations exhibit considerable variation from the summary curve. This supports the contention that size-survivorship data gleaned from ecological contexts should only be applied to the paleoecological record with extreme caution.