The present work was carried out in partial fulfillment of the requirements for the degree of Doctor ol Philosophy at the University of Cincinnati. The author Blends his sincere thanks to the members of the Departments of Biological Sciences and Geology at the University fur generously giving of their time and knowledge during the preparation of the manuscript. Especial thanks is extended to Dr. К. Е. Caster, under whose direction the manuscript was prepared. I le was a source ol help and en-tonragement, and his invaluable library made many rare «inks readily available to me. 1 am indebted to Dr. Norman П. Newell for reviewing the manuscript and offering many helpful suggestions. To my "wife continuing thanks for proofreading and typing the greater bulk of the manu-Mtipt.