Algal limestones were obtained from a number of localities in the course of a study of the geology of South Park made in the summers of 1934 and 1935 under the sponsorship of Northwestern University and assisted in 1935 by a grant from the Penrose Bequest of the Geological Society of America. The geology and stratigraphy of the region including a brief mention of the algal limestone are being given in a general report shortly to be published.1 The present paper is intended to give a more detailed description of the algal limestones, their distribution, structure, and conditions of deposition, and of the algae which assisted in their formation.
The author wishes to thank Professor C. H. Behre, of Northwestern University, for many courtesies extended in the course of the work. He also wishes to thank Dr. F. M. Van Tuyl and W. A. Waldschmidt, of the Colorado School . . .