CEPHALOPODA, of the Palæozoic formations Subgeneric, stratigraphical and geographical relations Orthocerata of the Schoharie grit Orthocerata of the Upper Helderberg limestone Orthocerata of the Hamilton group BACTRITES: History, and description of species GOMPHOCERAS: Historical sketch, distribution and generic relations PREFACE. The present publication constitutes the Second Part of Volume V of the PALEONTOLOGY OF NEW YORK. The volume contains descriptions and illustrations of the Gasteropoda, Pteropoda, and Cephalopoda of the Upper Helderberg, Hamilton, Portage, and Chemung groups. It was originally intended to include all the Mollusca of the classes Lamellibranchiata, Gasteropoda, Pteropoda and Cephalopoda of the above groups in a single volume; but a yet unfinished study of the first class has required eighty plates for its proper illustration, and for its final revision and completion several more plates will be necessary. The three other classes are here illustrated in one hundred and twenty plates, which still leaves some of the material in our collections unrepresented. Among the Cephalopoda a large proportion of the material is fragmentary and in the condition of casts of the interior, rendering the study more difficult and the illustrations far less satisfactory. Reference to this subject may be found in some remarks preceding the descriptions of the Orthocerata, and the same observations are applicable to all the Cephalopoda of the Schoharie grit. We are compelled to use such material, or to leave the species unillustrated for an indefinite period. The limestones of the Upper Helderberg and the shales of the Hamilton group afford more satisfactory material; but in the Portage and Chemung groups the collections are very fragmentary and unsatisfactory, and the results of the most careful study still leave much to be desired. Under these circumstances an author would prefer to wait for more complete collections; but the public are unwilling to appreciate this sentiment, and the State authorities, who represent the public, demand publication. It therefore only remains for the author to give the best results he has been able to obtain, leaving for those who may come after him the pleasure and satisfaction of producing a more complete work. Notwithstanding all these difficulties, the author is willing to believe that the students in geology will thank him for presenting to them, in the best dress possible, the imperfect material which would otherwise remain unavailable in their collections, and of no value to science or to scientific museums. The species described in this volume are illustrated by figures drawn and lithographed from original specimeus, which are chiefly in the State Museum collections, derived either from the original Geological Survey or from subsequent acquisitions; together with collections made by myself, or under my direction, and of specimens obtained from other authentic sources. The order and succession of the species, as presented in the plates of Gasteropoda, may not be strictly that which a systematically arranged conchological collection might require; but it is in accordance with the intention of the author, except in the few supplementary plates, and will be found to present a simple and natural order, so far as external form is concerned. In the Cephalopoda, the author has preferred to begin with the simple Orthoceratites, and to follow with those which present an external gradation of form, through the genera Gomphoceras, Cyrtoceras, Gyroceras, Trochoceras, Nautilus and Goniatites. Unfortunately, the earlier lithographed plates were arranged with a very incomplete knowledge of the material contained in the State collections, and this has necessitated the introduction of the simpler forms on the plates following the completion of the first arrangement, or from plate 74, ending with the Goniatites. This want of unity could not be avoided, but it affects only the plates-the text presenting the genera and species in consecutive order from page 217 to the end of the volume. In the preparation and final revision of the descriptions of the species of Cephalopoda I have been very ably assisted by Mr. C. E. Beecher, and in the proof-reading and preparation of the index to the volume I am indebted to Mr. J. A. Lintner. For the use of specimens in the study and illustration of the work I have been indebted to Prof. S. G. Williams, of Cornell University, from his private collection; to Dr. C. Rominger, of Ann Arbor, Michigan; to Dr. James Powers, of Lexington, and to Dr. Benjamin Rogers, of Pendleton, Indiana; to Dr. James Knapp, of Louisville, Kentucky, and to other gentlemen. There are other collections within the State of New York which would have helped to elucidate the character and structure of certain forms, and I can only regret that these could not have been placed in my hands for study. The collections of the late Ledyard Lincklæn, originally deposited in the State Museum, and subsequently presented to the institution by Mrs. Lincklæn, have afforded some interesting specimens from the Goniatite Limestone of the Marcellus Shale and Hamilton Group. The collections purchased by the State from Mr. John Gebhard, have furnished the greater part of all the specimens of species coming from Schoharie, and especially those of the Schoharie grit and the Goniatite limestone of that locality. December, 1879. JAMES HALL. |