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Recent paleoecological studies have emphasized the recognition of successional stages of level‐bottom communities, but have neglected to point out techniques for distinguishing succession within a fossil community from the temporal and spatial replacement of one fossil community by another. The physical integrity of a marine level‐bottom community is discernible, in most instances, through careful temporal and spatial study, and one community can be distinguished from another by judicious application of the ‘end‐member’ concept. Community boundaries are only as distinct as the associated environmental stress gradient. Of first‐order significance in understanding fossil community succession and replacement is appreciation of the basic asymmetry of the community dynamics involved in transgression‐regression events. Of second‐order importance is appreciation of the nature of the onshore‐offshore environmental stress gradient, which, in turn, is controlled by the physical setting of transgression‐regression (e.g. progradation versus eustatic control; high topographic relief versus low topographic relief, etc.). The application of the preceding concepts is shown by detailed study of community succession and replacement in the Cambridge Limestone (Upper Pennsylvanian), Guernsey County, Ohio.

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Thin sections from 44 sherds representing eight prehistoric sites on four islands (Barbuda, Montserrat, Anguilla, St. Martin) in the northern Lesser Antilles (West Indies) were examined using a petrographic microscope. Point counting distinguished three temper associations: (1) exclusively volcanic,(2) volcanic and carbonate, and (3) volcanic, carbonate, and grog. Exclusively volcanic or dominantly volcanic (with low carbonate) temper associations occur in all Saladoid and many post‐Saladoid sherds, with plagioclase feld‐spar and volcanic rock fragments being most abundant. Thin sections with significant carbonate content or with grog were restricted to post‐Saladoid sherds from Barbuda and to a lesser extent Anguilla. the presence of volcanic grains in sherds from the limestone islands of Barbuda and Anguilla indicates that volcanic islands in the region served as sources of pottery (or volcanic temper) for these two islands.

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Meadowcroft Rockshelter is a deeply stratified multicomponent site in Washington County, southwestern Pennsylvania. The 11 well-defined stratigraphic units identified at the site span at least 16,000 years and perhaps 19,000 years of intermittent occupation by groups representing all of the major cultural stages/periods now recognized in northeastern North America. Throughout the extant sequence, the site served as a locus for hunting, collecting, and food-processing activities, which involved the seasonal exploitation of the immediately adjacent Cross Creek Valley and contiguous uplands. Presently, Meadowcroft Rockshelter represents one of the earliest well-dated evidences of man in the New World as well as the longest occupational sequence in the Western Hemisphere.

Ever since the publication of the first of more than 50 internally consistent radiocarbon dates from Meadowcroft Rockshelter (36 WH297), controversy has been generated by frequent assertions that the dates older than 11,000 B.C. have suffered particulate or nonparticulate contamination. Data bearing on these assertions are assessed in the light of accelerator mass spectroscopy (AMS) dates provided by Oxford University. The weight of all data taken together suggests that this site still represents the best-dated evidence for the presence of human beings south of the glacial front in the Americas. That evidence indicates that Native Americans were present in southwestern Pennsylvania by 14,000–14,500 years ago.