Afternoon Session, August 24. 



The Society reassembled at 2:20 p. m. 

 The first paper read was : 



THE LOWER SILURIAN (oRDOVICTAN) ICHTHYIC FAUNA AND ITS MODE OF 



OCCURRENCE. 



BY C. D. WALCOTT. 



This paper was dicussed by Dr. Friedrich Schmidt, Professor E. W. 

 Claypole, Professor E. D. Cope, Dr. Karl von Zittel, Dr. Otto Jaekel, and 

 the author. It is printed elsewhere in this volume. 



The following paper was then read : 



THE PLANT-BEARING DEPOSITS OF THE AMERICAN TRIAS. 



BY LESTER F. WARD. 



Contents. 



Introduction page 23 



American Distribution 26 



Foreign Distribution 28 



General Conclusions from foreign Distribution 31 



Introduction. 



Having been requested by the Director of the United States Geological Survey to 

 prepare an essay on the correlation of the American plant-bearing deposits of the 

 United States, so far as indicated by their respective floras, I entered upon this work 

 in February, 1888, and have continued it as opportunity permitted to the present 

 time. The formations were taken up in their order of succession, beginning with 

 the lowest, and the treatment of the Paleozoic horizons was completed, subject to 

 revision, in July, L889. The Trias was then taken up and brought to a conclusion 

 near the end of L890. The next higher Mesozoie floras are now in hand. 



The plan of treatment lias been to give first a historical account of the discovery 

 of vegetable remains in each formation, followed by such citations of opinion relative 

 to its age as will show the progress hitherto made in fixing its geological position, 

 and then to c pile and discuss the paleontologieal data, and make thorough com- 

 parisons of each flora and florule with all others that contain the same or similar 

 vegetable forms. 



In the present paper I shall confine myself to the Triassic deposits of the United 

 States, as having an especial interest from this point of View: first, because their 

 precise age has been much discussed and lias not Keen definitely settled ; and sec- 

 ondly, because 1 1 j * - paleontologieal data, meager in all departments, consisl so 

 hugely of fossil plants. 



