Smithsonian Miscellaneous Collections
SMITHSONIAN MISCELLANEOUS COLLECTIONS VOLUME 57, NUMBER 6 CAMBRIAN GEOLOGY AND PALEONTOLOGY II No. 6.-MIDDLH CAMBRIAN BRANCHIOPODA, MALACOSTRACA, TRILOBITA, AND MEROSTOMATA With Plates 24 to 34 BY CHARLES D. WALCOTT TUBLICATION 2051) CITY OF WASHINGTON PUBLISHED BY THE SMITHSONIAN INSTITUTION MARCH 13, 1912 €5e Bnvi) (^aitimovi (preee BALTIMORE, Mn., U. S. A. CAMBRIAN GEOLOGY AND PALEONTOLOGY II No. 6.—MIDDLE CAMBRIAN BRANCHIOPODA, MALACOSTRACA, TRILOBITA, AND MEROSTOMATA By CHARLES D. WALCOTT (With Plates 24 to 34) CONTENTS PAGE Introduction 148 Habitat 149 Character of the shale 149 Mode of occurrence 151 Classification 153 Stratigraphic distribution 155 Structural features 157 Exoskeleton 157 Labrum 1 58 Segmentation 1 58 Appendages 1 58 Alimentary canal 160 Hepatic caeca 160 Origin of Middle Cambrian crustacean fauna 160 Relation to recent crustaceans 164 Survival of the Branchiopoda 165 Class Crustacea 166 Sub-Class Branchiopoda j66 Order Anostraca Caiman 166 Family Opabinidse, new family 166 Genus Opabinia, new genus 166 Opabinia regalis, new species (pis. 27, 28.) 167 Appendages 167 Interior structure 168 Dimensions 168 Female 169 Opabinia ? media, new species 1 70 Genus Leanchoilia, new genus 170 Smithsonian Miscellaneous Collections, Vol. 57 No. 6 145 i 146 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 57 PAGE Leanchoilia superlata, new species (pi. 31) 170 Genus Yohoia, new genus 171 Yohoia tenuis, new species (pi. 29) 172 Appendages 1 72 Dimensions 1 73 Yohoia plena, new species (pi. 29) 1 73 Genus Bidentia, new genus 173 Bidentia difUcilis, new species (pi. 30) 174 Appendages 1 74 Dimensions 1 74 Order Notostraca 1 75 Family Naraoidse, new family 175 Genus Naraoia, new genus 1 75 Naraoia compacta, new species (pi.
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