The Journal of Geology, published by the University of Chicago Press, presents timely research on all aspects of geology including paleontology, mineralogy, petrology, and geochemistry. The Journal also features reviews, discussions, and comments on recent publications and developments within the field. Its content is essential reading for professionals and academics in the earth sciences. This work has been selected by scholars as being culturally important, and is part of the knowledge base of civilization as we know it. This work is in the "public domain in the United States of America, and possibly other nations. Within the United States, you may freely copy and distribute this work, as no entity (individual or corporate) has a copyright on the body of the work. Scholars believe, and we concur, that this work is important enough to be preserved, reproduced, and made generally available to the public. We appreciate your support of the preservation process, and thank you for being an important part of keeping this knowledge alive and relevant.