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. . . .