Long slender straight and slightly curved nautiloids are of widespread occurrence in the Early Paleozoic of the United States, Canada, and Newfoundland. They appear in the Lower Ozarkian and are abundant in the Upper Ozarkian and the Upper Canadian. A few species are known from contemporaneous beds in Greenland, northwestern Europe, eastern Asia, and probably Australia and South America. Externally most of the American forms are similar, though some are smooth and others are annulated. Chiefly on the basis of the figure of the conch, the nature of the surface, the shape of the sutures, and particularly the structure of the siphuncle they have been divided into eleven families: the Stemtonoceratidae (3 species representing 2 genera), the Endocycloceratidae (5 species, 2 genera), the Bassleroceratidae (41 species, 10 genera), the Rudolfoceratidae (8 species, 3 genera), the Orthocerotidae (20 species, 7 genera), the Robsonoceratidae (2 species, 1 genus), the Spyroceratidae (29 species, 3 genera), the Endoceratidae (70 species, 9 genera), the Suecoceratidae (3 species, 1 genus), the Bathmoceratidae (1 species, 1 genus), and the Eothinoceratidae (1 species, 1 genus). All but four of these families are represented in both the Ozarkian and the Canadian, and these four contain only a few aberrant forms.

More than half of the known specimens of Ozarkian and Canadian cephalopods are brevicones. They are of widespread occurrence and are locally abundant in the United States, Canada, and Newfoundland. In age they range from Lower Ozarkian to uppermost Canadian, but the bulk of those now at hand come from the Middle and Upper Ozarkian and the Upper Canadian. Comparatively little knowledge is available in regard to related faunas outside of North America, but such occur in both western Europe and eastern Asia. Most of the known forms axe superficially similar. They vary chiefly in the shape of the conch and the nature of the siphuncle. Primarily on the basis of these features, they have been divided into four families: the Piloceratidae (37 species representing 6 genera), the Cyclostomieeratidae (9 species, 3 genera), the Cyrtendoceratidae (141 species, 13 genera), and the Beekmanoceratidae (1 species, 1 genus). It is perhaps significant that the great majority of our specimens fall readily into one of two groups, the Cyrtendoceratidae, characteristic of the Middle and Upper Ozarkian, and the Piloceratidae, essentially limited to the Upper Canadian.

Coiled nautiloids are not known to occur in the Ozarkian but are widespread in the Upper Canadian of North America. The best preserved and most diversified faunas are from the Lake Champlain region. Also, numerous specimens have been collected at several localities in western Newfoundland and the Mingan Island area. The Southern Appalachian and the Ozark regions have yielded a sequence of faunas which are locally well represented. These few areas constitute all the important occurrences, and only a very small number of questionable specimens are known outside of North America. All the Canadian nautilicones are rather unspecialized forms with orthochoanitic siphuncles. They vary chiefly in the shape of the conch and the position of the siphuncle. Primarily on the basis of these features, they have been placed in four families: the Deltoceratidae, Plectoceratidae, Tarphyceratidae, and Trocholitidae. Altogether about 75 species are now known, and these are being referred to 17 genera.

INTRODUCTION AND ACKNOWLEDGMENTS Over many years the senior author, assisted by other members of the United States Geological Survey, has accumulated many brachiopods from the Ozarkian and Canadian periods. In 1931 the junior author joined in the study of these collections. Before the study was undertaken, about 170 species of brachiopods representing about 24 genera were known. The authors have added 32 genera and have increased the number of species to 319. In addition to the above mentioned specimens a large collection was studied which was made by C. D. Walcott. All regions of Ozarkian and Canadian strata known in North America, except Newfoundland, are represented in the collections. It is a pleasure to acknowledge gratefully the kind assistance received from the Geological Society of America through a grant from the Penrose Bequest. This grant enabled the authors to have the illustrations prepared and permitted the junior author to visit the National Museum of Canada in order to study Billings’ brachiopod types from Lévis, Quebec. Special thanks are due Dr. Edwin Kirk of the United States Geological Survey who generously loaned large collections of brachiopods from the Great Basin and adjacent country. The authors are also indebted to Dr. Charles Butts, formerly of the United States Geological Survey, who furnished a number of the specimens from the southern Appalachians. Dr. Josiah Bridge of the United States Geological Survey and Mr. It. D. Mesler assisted in many ways and supplemented the collections by fine material. Acknowledgments are also due Dr. E. . . .

FORMATION NAMES A chart (PI. 58) showing the correlation of the Ozarkian and Canadian formations of the eastern half of United States and Canada and western Newfoundland represents the most recent views of the senior author. A lden F ormation —lower half of Upper Canadian of Oklahoma, containing Ceratopea faunules. A rbuckle L imestone —a great sequence of limestones ranging in age from middle Upper Cambrian to youngest Upper Canadian. This term should be discarded as too inclusive and indefinite. The original contents of the “formation” have already been divided into 12 formations, four of them (Honey Creek, Fort Sill, Royer dolomite, and Signal Mountain) being of Upper Cambrian age; four of them (Chapman Ranch formation, McKenzie Hill limestone, Wolf Creek dolomite, and Gasconade) being of Ozarkian age; and the remaining four beginning with an otherwise unnamed Lower Canadian limestone, 1100 feet in thickness, Cool Creek limestone (Middle Canadian) 600 to 1200 feet, and two Upper Canadian formations—the Alden limestone, marked by a number of Ceratopea zones and the more thinly bedded West Spring Creek limestone—with a combined maximum thickness exceeding 3300 feet. When the desired information is available the “Arbuckle limestone” fossils described or mentioned are referred to the particular formational unit from which they were collected. Faunas, at times, of northern, at other times, of southern origin. A xeman L imestone —a fossiliferous, pure, Upper Canadian limestone, 158 feet thick, at Bellefonte, Pennsylvania. Here it rests on about 500 feet of dolomite containing unquestionable Cotter fossils; it is succeeded by the Bellefonte . . .

The principles and practice of sequence stratigraphy are of ancient heritage. In North America, the separation of the Carboniferous into two systems and the identification of Ozarkian and Comanchean and other indigenous chronostratigraphic entities were efforts toward making the segmentation of the geologic column more representative of stratigraphic observations, particularly on cratons and their margins. Growing awareness of the influence of tectonics on sedimentation, as well as recognition that unconformity-bounded sedimentary packages identified in Montana were craton-wide, led to this writer’s 1948 GSA paper which formally applied Native American tribe names to sequences as lithostratigraphic units. Acceptance of the sequence philosophy beyond the Northwestern campus lacked early manifestations of fervor and enthusiasm, although isolated pockets of true believers were known to exist. Except for papers by me, my students, and the late, lamented H. E. Wheeler, sequences did not appear in the public prints for more than a decade—and then through misappropriation by the U.S. Geological Survey. The list of Indian-tribe sequences was emended and completed at another GSA presentation in 1959. Meanwhile the sequence concept was alive and well in a research facility of a company later to be known as Exxon. Here, Peter Vail and a cohort of preconditioned colleagues seized upon the stratigraphic imagery made available by multichannel, digitally recorded, and computer-massaged reflection seismography to establish the discipline of seismic stratigraphy. The “Vail curve,” recording relative change of coastal onlap, defines successive “sequences” which are the third-order bottom rungs of an elaborate hierarchy that is topped by “megacycle sets,” themselves subdivisions of the ancestral sequences. The taxonomy of sequence stratigraphy is not at issue (although it has been complicated by the sanctification of “synthem” by the International Subcommission on Stratigraphic Classification). Interpretation is important, however; the Exxon people, their alumni, and adherents see sea-level change as the “be-all” and “end-all” of coastal onlap and its erosional and depositional concomitants. No one will question the influence of sea-level change on many of the observations that make sequence stratigraphy viable, but there are distinctions among and within major-scale unconformity-bounded stratal packages that can be explained only by tectonic change. Whether tectonic influence can be extended to Exxonian sequences remains to be demonstrated. Meanwhile, it is worth considering the proposition that sea-level change is a second- or third-order response to some more significant global phenomenon.

Abstract The controversial concepts of Edward Oscar Ulrich (1857–1944) dominated American stratigraphy during the first decades of this century. His U.S.G.S. mapping experience and extensive knowledge of the paleontology and stratigraphy of North America culminated in his masterwork: Revision of the Paleozoic Systems (1911) and several late papers (1916, 1920, 1924). The revision, which served as a guide to a generation of geologists, also contains Ulrich’s philosophy of correlation. Application of his geological concepts to American stratigraphie successions led Ulrich to propose radical changes in existing classifications and correlations. Among his more controversial proposals were the creation of two new lower Paleozoic time stratigraphie units of systemic rank, the Ozarkian and the Canadian; a theory of oscillating troughs and barriers to explain the occurrence of the shelly carbonate and graptolitic shale facies in adjacent strike belts in the Appalachians; and the revision of the Croixan Series of the Upper Mississippi Valley. Each of these proposals was incorporated in various textbooks and correlation charts of the period. However, as detailed stratigraphie studies in the Ozarks, the Upper Mississippi Valley, and in the Appalachians were completed, it was found that Ulrich’s concept of correlation was untenable and it was gradually replaced by one stressing facies relations. But, because of his authority, his disputative nature, and the tenacity with which he held his views, the development of American stratigraphy had been hampered.

Abstract Natural gas is produced in the states of New York and Pennsylvania from rocks of Pennsylvanian, Mississippian, Devonian, Silurian, Ordovician, and Ozarkian age. The limits of production are defined in Pennsylvania by the highly folded and faulted area in the central part of the state and in New York by the Adirondack Mountains and the valley of the Hudson. From a historic standpoint this region is very interesting since the first natural gas well was drilled and the first natural gas transmission line was laid in this area. The stratigraphy of the area covers almost the entire Paleozoic system of rocks. These rocks were deposited in the northern end of the Appalachian geosyncline. The most important gas-producing horizons represent shore-line deposits or the fine sand deposits of deltas or partly enclosed bays. There are more than 50 gas-producing horizons and more than 200 separate gas fields in the area. The dominating structural features are the Appalachian geosyncline and the system of folds and faults which originated during the Taconic and Appalachian revolutions. Gas occurrences in certain sandstones conform very closely to structural conditions but in general the character of the reservoir rocks is the most important factor in determining the accumulation of gas. The carbon ratio of the coals is an excellent index of the presence of oil or gas in the sandstones, but recent studies of certain of the more important reservoir rocks of the Chemung formation indicate that the permeability of the sandstone is of greater importance in limiting the area of oil production than the metamorphism of the rocks which was responsible for the progressive eastward devolatilization of the coals. The supply of gas in this part of Pennsylvania at present exceeds market demands, whereas for several years New York's production has been supplemented by large amounts of imported gas. The proved reserves of the Pennsylvania fields combined with the large reserves of neighboring states should be ample to supply the demands of this territory for many years.