NO. 2 PRE-CAMBRIAN ALGONKIAN ALGAL FLORA 79 



INTRODUCTION 



This is a preliminary paper on a fossil algal flora from the Algon- 

 kian formations of the Cordilleran area of western America. What 

 has been found as yet appears to have been formed through the 

 agency of algse closely allied to the Cyanophyceae (Blue-green Alg?e) . 

 The associated fauna as it occurs in the Belt series of Montana is 

 illustrated on Plates 21 and 22. 



The subject matter is divided into a geologic and a biologic section. 

 The first gives a brief outline of continental conditions and sedimen- 

 tation of Algonkian time, and the second deals with the algal flora 

 and the traces of a contemporaneous aquatic fauna. 



There are a number of algal forms known to me from the Cam- 

 brian formations that are allied to Cryptosoon and Collenia which 

 will not be referred to further in this preliminary paper on the 

 Cordilleran pre-Cambrian forms. The field of investigation is a 

 large one, however, and promises most interesting results. 



Acknowledgments. — I am indebted to Mr. M. Collen, who has a 

 ranch on the eastern slope of the Big Belt Mountains south of White 

 Sulphur Springs, for observations on the occurrence of the algal 

 flora in the Newland limestone and Spokane shales. Mr. Collen 

 called my attention to the remarkable forms in the Newland lime- 

 stone, and made a large collection of material for the United States 

 Geological Survey. I have given his name to a genus that occurs 

 in the Spokane shales in recognition of his great interest and for 

 his persevering search to explain the origin and mode of occurrence 

 of the fossil remains that he suspected to be corals. 



In connection with the search for microscopic characters of the 

 algffi, Dr. Albert Mann of Washington took the greatest interest 

 and first discovered cells of the type of those of the Cyanophyceae, 

 Blue-green algse (pi. 20, fig. 2), and notwithstanding his many 

 duties made the micrographs of the chains and groups of cells. 

 In the later part of this work he was ably assisted by Mr. Charles 

 Resser of the United States National Museum. 



Dr. Charles A. Davis of the Bureau of Mines very kindly advised 

 in relation to the recent fresh-water algje and their calcareous 

 deposits and called my attention to the remarkable bank deposits in 

 the lakes of Michigan and New York State. 



To Dr. John M. Clarke, State Geologist of New York, I am in- 

 debted for a small collection of the Lake Balls from Canandaigua 

 Lake. New York, and the electrotype of plate 16. 



