Doctor MacDonald's reports to the Canal Commission have been published in the annual reports of the chairman of the Canal Commission; and he is the author of a more lengthy paper entitled "Some engineering problems of the Canal Zone in their relation to geology and topography," published as Bulletin 86 of the United States Bureau of Mines. Since the termination of his services for the Canal Commission he has completed a large report on the physiography, stratigraphic and structural geology, petrography, and economic geology of the Canal Zone. The transmission of this memoir for publication has been delayed because some of the paleontologic determinations were needed for interpreting the geologic history. After the agreement to the proposed plan of cooperation, I took charge for the United States Geological Survey of the preparation of the special paleontologic reports, of the problems of geologic correlation, and of the coordination of the investigations with other work on the physiography, stratigraphy, paleontology, and geologic history in the southeastern United States and the West Indies. The paleontologic material was sorted according to groups, and the following specialists undertook monographic reports: Dr. Marshall A. Howe, calcareous algae. Dr. Joseph A. Cushman, foraminifera. Dr. T. Wayland Vaughan, madreporarian corals. Dr. C. Wythe Cooke, mollusca. Mr. F. Canu and Dr. R. S. Bassler, bryozoa. Prof. H. A. Pilsbry, cirrepedia. The few vertebrates obtained were identified by Mr. J. W. Gidley. All of the paleontologic reports are now complete except that on the mollusks. It was at first hoped that Dr. W. H. Dall would prepare the one on this group, but pressure of other work prevented him. Later Dr. C. Wythe Cooke, paleontologist of the United States Geological Survey, began a study of the collection of mollusks, but other duties have interfered with his prosecution of it. The recent papers by Toula2 and by Brown and Pilsbry3 have been used, and they are valuable, but they do not meet the needs of the present investigation, for the material described in them mostly represents one geologic formation, the Gatun formation, and the stratigraphic 1 U. S. Bureau Mines Bull. 86, pp. 88, 29 pls., 9 text figs., 1915. Toula, Franz, Eine jungtertiäre Fauna von Gatun am Panama-Kanal, Geolog. Reichsanstalt Wien Jahrb., vol. 58, pp. 673-760, pls. 25-28, 15 text figs., 1909; Die jungtertiäre Fauna von Gatun am PanamaKanal, Ibid., vol. 61, pp. 487-530, pls. 30, 31, 1911. Brown, Amos P., and Pilsbry, Henry A., Fauna of the Gatun formation, Isthmus of Panama, Acad. Nat. Sci. Phila. Proc. for 336-373, pls. 22-29, 3 text figs., 1911; Fauna of the Gatun formation, Isthmus of Panama ! Phila. Proc. for 1912, pp. 500-519, pls. 22-26, 5 texts figs., 1913. data are not sufficient. It is probable that three and perhaps four horizons will be discriminated within the Gatun formation. Other groups of organisms are adequate for correlation purposes in most or all of the other geologic formations, but for the Gatun formation the principal reliance must be placed on the mollusks. The collections of mollusks made by Doctor MacDonald and myself is very extensive, and the greatest possible care was taken in obtaining full information on the stratigraphic relations of the material. It is hoped that a report commensurate with the size and importance of the collection may not be much longer delayed. The series of papers here presented comprises all of the paleontologic memoirs that have been completed. These are immediately followed by descriptions of the geologic exposures where collections of fossils were made, with summaries of the fossils according to their stratigraphic occurrence, and a chapter on the geologic correlation of the fossiliferous formations, both with other American and with European formations. It is intended that Doctor MacDonald's comprehensive general report will be published soon after this series of memoirs has been issued. The names of the geologic formations used in the paleontologic reports are the same as those employed by Doctor MacDonald in Bulletin 86 of the United States Bureau of Mines, to which reference is made on page v of this preface. I wish to thank the officials of the Canal Commission, particularly Maj. Gen. Goethals, Director George Otis Smith, and Chief Geologist David White of the United States Geological Survey, and Dr. Charles D. Walcott, Secretary of the Smithsonian Institution, for the support they have given these investigations. To my colleagues outside the Geological Survey and United States National Museum, Dr. Marshall A. Howe, Prof. E. W. Berry, Dr. Robert T. Jackson, Mr. F. Canu, and Prof. H. A. Pilsbry, who has collaborated in this work, I am under deep obligations; and it is a pleasure to record my appreciation of the efforts of my official colleagues, Dr. D. F. Mao Donald, Dr. Joseph A. Cushman, Dr. C.Wythe Cooke, Dr. R. S. Bassler, Dr. Mary J. Rathbun, and Mr. J. W. Gidley, all of whom have labored harmoniously to bring a large undertaking to a successful conclusion. THOMAS WAYLAND VAUGHAN. SEPTEMBER 15, 1919. CONTENTS.1 Page. ON SOME FOSSIL and recent LITHOTHAMNIEAE OF THE PANAMA CANAL ZONE. Introduction... Descriptions of species. Archaeolithothamnium episporum.. Lithothamnium vaughanii.... isthmi.. 112268 For the most part the papers in this volume have individual indexes following the plates at the end of |