CAMBRIAN GEOLOGY AND PALEONTOLOGY 



III 



No. 2.— PRE-CAMBRIAN ALGONKIAN ALGAL FLORA 



By CHARLES D. WALCOTT 



(With Plates 4 to 23) 



CONTENTS PAGE 



Introduction 79 



Acknowledgments 79 



Continental conditions during Algonkian time 80 



Diastrophism 82 



Narrowing of the Cordilleran sea 82 



Coastal deposits 83 



Cambrian basal unconformity 83 



Climate 83 



Origin of Algonkian limestones 84 



Recent calcareous deposits 85 



Algonkian lakes 89 



Deposition of limestone through the agency of alg?e 89 



Bacterial deposits , 92 



Application 94 



Magnesian limestones 95 



Definition of magnesian limestone and dolomite 96 



Magnesian limestone 96 



Dolomite 96 



The biotic record 97 



The fauna 97 



Algal deposits 98 



Stratigraphic position 99 



Section of Belt Series 99 



The algal flora 100 



Comparison of recent Blue-green alg;e deposits and those of Algon- 

 kian time 100 



Mode of growth loi 



Mineral composition 102 



Microscopic structure 102 



Bacteria 103 



Classification 103 



Description of genera and species 104 



Newlandia, new genus 104 



NewJandia concentrica, new species (pi. 5, figs. 2, 3) 105 



Newlandia frondosa, new species (pi. 5, fig. 4; pi. 6, figs. 1-3; pi. 7, 



figs. I, 2 ; pi. 8, figs. 1-3) 105 



Smithsonian Miscellaneous Collections, Vol. 64, No. 2 



77 



