to those belonging to the Taconic system. These additions have been made only in cases which required them; or, at least, where descriptions and figures of them could not be found. While executing this work, I did not expect that I should be able to secure perfect accuracy, hut I am able to say, when the volume is finished, that I have put in requisi tion all the means within my reach, to secure an end so desirable. As it is, 1 submit the work to the student with the hope that it will prove a useful guide in the study of American Geology. EBENEZER EMMONS. Albany, Sept. 20th, 1855.