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Smithsonian Miscellaneous Collections SMITHSONIAN MISCELLANEOUS COLLECTIONS VOLUME 67, NUMBER 4 CAMBRIAN GEOLOGY AND PALEONTOLOGY IV No. 4—APPENDAGES OF TRILOBITES (With Plates 14 to 42) BY CHARLES D. WALGOTT (Publication 2523) CITY OF WASHINGTON PUBLISHED BY THE SMITHSONIAN INSTITUTION DECEMBER 1918 ZU Boro Qgattimott (p«ee BALTIMORE, MD., U. S. A. CAMBRIAN GEOLOGY AND PALEONTOLOGY IV No. 4.—APPENDAGES OF TRILOBITES By CHARLES D. WALCOTT (With Plates 14 to 42) . CONTENTS page Introduction 116 Acknowledgments 1 18 Correction for Volume 57 118 Section i Notes on species with appendages up Mode of occurrence up Conditions of preservation 121 Manner of life 123 Method of progression 124 Food I25 Defense and offence 125 Description of species with appendages 126 Neolenus serratus (Rominger) 126 Cephalic appendages 127 Thoracic appendages 128 Kootenia dawsoni (Walcott) 131 Asaphidse Burmeister 132 Isotelus maximus Locke 133 Isotelus covingtonensis Ulrich ? MSS 134 Triarthrus becki Green 135 Development 143 Ptychoparia cordillerce (Rominger) 144 Ptychoparia permulta, new species 145 Calymene senaria Conrad 147 Ceraurus pleurexanthemus Green 148 Cephalic limbs 149 Thoracic limbs 1 50 Odontopleura trentonensis (Hall) 153 Trinucleus concentricus Eaton 153 Ordovician crustacean leg 154 Smithsonian Miscellaneous Collections, Vol. 67, No. 4 "5 Il6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 67 Section 2 Structure of the trilobite 154 Dorsal shield 1 54 Ventral integument 155 Intestinal canal 156 Appendages 158 Limbs 158 Cephalic 160 Thoracic 160 Pygidial 161 Summary , 161 Position of the limbs 162 Respiration of the trilobite 164 Restoration of ventral appendages 165 Restoration of thoracic limbs 166 Comparison with crustaceans 167 Tracks and trails of trilobites 174 Index 217 ILLUSTRATIONS Plates 14-42 180-216 Text figs. 1, 2, 3 171, 172 INTRODUCTION In September, 1873, I said to Professor Louis Agassiz that if opportunity offered I would undertake as one bit of future research work to determine the structure of the trilobite. This promise has kept me at the problem for the past forty-five years, and except for the demands of administrative duties the investigations would have been advanced much more rapidly. Since 1873 I have examined and studied all the trilobites that were available for evidence bearing on their structure and organization. The first summary of results was published in 1881 * and a restoration and cross-sections given of the ventral surface of Calymene senaria (loc. cit., pi. VI) based on sections cut through the test, ventral cavity and appendages. These proved that the trilobite had a pair of biramous appendages for each segment of the thorax and abdomen and four pairs of cephalic appendages, the enlarged proximal joints of which served as organs of manducation. The restorations have since been shown to be essentially correct with the possible exception of the enlargement of the terminal joints of the posterior cephalic 1 The Trilobite : New and Old Evidence Relating to its Organization. Bull. Mus. Comp. Zool., Cambridge, Mass., Vol. VIII, No. 10, 1881, pp. 191-224, pis. I-VI. NO. 4 APPENDAGES OF TRILOBITES 117 legs and the too short, proximal joints (protopodites). The placing of the Trilobita under the Class Pcecilopoda in 1881 was changed in 1 1894 when it was suggested that the Trilobita, Entomostraca, and Malacostraca were descendent from a common ancestor of pre- 2 Cambrian time. In 1912 the Trilobita were represented as descen- dent from the Branchiopoda and on the line of descent of the Mero- stomata. The presence of antennules was not known positively until 3 Valiant discovered antennules on Triarthrus in 1892, and caudal rami until Walcott found them on Neolenus twenty years later.* During the field seasons of 1910 to 1913 and 1917 I collected from the Burgess shale member of the Middle Cambrian Stephen forma- tion of British Columbia with the aid of assistants a large fauna including specimens of the highly organized trilobite Neolenus serratus, some of which have beautifully preserved ventral appen- dages. Neolenus has a large head and tail, a short compact thorax, and is far advanced in the development of the Trilobita. Always hoping for more perfect specimens, a detailed description with illus- trations was deferred, and only a few of the best specimens photo- 5 graphed and incidentally used in illustrations. More data are desired, but I have decided to now record the evidence at hand as the Burgess shale quarry on the ridge connecting Mounts Wapta and Field is about exhausted and only a new locality or a chance specimen in the debris from the quarry will give further material from there for study. For a description of the Burgess shale and the mode of occurrence of fossils the reader is referred to notes published in 191 2* In this paper I stated that [p. 192] In the near future I wish to review the conclusions published in my paper 7 of 1881, and those that have been entertained regarding Triarthrus becki and the new material from the Burgess shale. As it is not probable that I shall again write on the structure of the trilobite I am now assembling in this paper notes and illustrations on the material studied from time to time since 1894. This includes the 1 Proc. Biol. Soc. Washington, Vol. IX, p. 94. 2 Smithsonian Misc. Coll., Vol. 57, p. 164. 8 The Mineral Collector, New York, Vol. 8, No. 7, 1901, pp. 105-112. 4 Smithsonian Misc. Coll., Vol. 57, 1912, p. 208, pi. 24, figs. 1, 10. 5 Idem, 1911, pi. 6, figs. 1, 2 ; 1912, pi. 24, figs. 1, la; pi. 45, figs. 1, 2, 3, 4. Text-book Pal. (Zittel), Eastman 2d ed., 1913, Vol. I, p. 701, fig. 1343, p. 716, figs. 1376, 1377. * Smithsonian Misc. Coll., Vol. 57, pp. 149-153. 7 The Trilobite, New and Old Evidence relating to its Organization. Bull. Mus. Comp. Zool., Harvard Coll., Vol. VIII, 1881, pp. 208-211. Il8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 67 specimens of the Cambrian genera Neolenus, Kootenia, and Ptycho- paria and the Ordovician genera Calymene, Ceraurus? Isotelus, and 2 Triarthrus Of these, Neolenus has given the best and most instruc- tive material of a trilobite in advanced development, and Triarthrus of a more primitive form. The discussion of the appendages found in the several genera follows the description of the material known to me of each of the genera mentioned. In a memoir soon to go to press by Dr. Percy E. Raymond I under- stand there will be a very complete statement of Beecher's work and a full review of what is known of the trilobite. ACKNOWLEDGMENTS I am indebted to the Museum of Comparative Zoology, Harvard University, for the opportunity of studying the Walcott collection of Calymene senaria and Ceraurus pleurexanthemus showing appen- dages. To the Peabody Museum, Yale University, for the loan of a portion of the Beecher collection of Triarthrus becki. To several assistants in the field collecting at Burgess Pass, notably Dr. Lan- caster D. Burling, now of the Geological Survey, Canada. Mr. R. D. Mesler, of the U. S. National Museum, and to the members of my family who worked with me during several field seasons. In the office, Mr. Clarence R. Shoemaker, of the U. S. National Museum, made»the final drawings of the restorations of the ventral surface of Neolenus, Calymene, and Triarthrus, using his knowledge of the Crustacea to give a less diagrammatic appearance to my outline sketches. Mrs. Mary V. Walcott retouched the photographs used in illustration on plates 14, 18, 19, 20, 22, and 23. Miss G. R. Brigham, Ph. D., lettered the plates and read the text-proofs. CORRECTION In 191 1 1 referred figures 2 and 3, plate 2, also text figure 10, p. 206 (1912), of Emeraldella brocki to Sidneyia inexpectans in the paper 3 on the latter species. At the time I had not thoroughly studied E. brocki, and assumed that the specimens before me belonged to Sidneyia. In both cases the reference should be to Emeraldella. I expect in the near future to revise my preliminary work on the crustaceans from the Burgess shale. 1 Through the courtesy of the Museum of Comparative Zoology, Harvard College. 2 Through the courtesy of the Peabody Museum, Yale University, and the U. S. National Museum. 8 Smithsonian Misc. Coll., Vol. 57, 1911. NO. 4 APPENDAGES OF TRILOBITES 1 19 SECTION 1 NOTES ON SPECIES WITH APPENDAGES Mode of Occurrence 1 The two species of Ordovician Trilobites, Calymene senaria and Ceraurus pleurexanthemus, from which nine-tenths of the sections illustrating appendages were obtained, are the two most abundant forms in the Trenton limestone of Central and Northern New York. Their remains, or those of representative species, occur, usually in a fragmentary condition, in nearly every layer of the Trenton lime- stone, and range, above, into the Cincinnatian and, below, into the Black River limestone. Their geographic distribution is also great, as they occur in the Eastern Canadas and at nearly all the exposures of the Trenton series in the Northern United States, as far west as the Mississippi River. Calymene is much more abundant iri Ohio, but at the locality from which the specimens of Ceraurus preserving appendages were obtained, the latter far exceeded it in numbers. The special interest attached to the occurrence of both species near Trenton Falls, Oneida County, New York, as well as of several other species, is their very perfect state of preservation in a thin layer of limestone outcropping in a small ravine half a mile east of the Trenton Falls canyon or gorge in the Township of Russia, Herkimer County, New York. An examination of the same horizon that this bed occupies, for several miles along the canyon, which is but half a mile away at one point, failed to give a single entire trilobite, and the fragmentary remains are rare.
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