564 Wm. F. Prouty — Meso-Silurian Deposits of Maryland. 



place careful measured sections and fossil collections have 

 been . made. With the exception of the Ostracods and Bryo- 

 zoa, the fossil study has been practically completed. In the 

 pursuance of his work the author has had access to the collec- 

 tions of the National Museum, the New York Museum of 

 Natural History, the New York State Collection at Albany, 

 and several smaller and private collections. He is also greatly 

 indebted to Prof. Schuchert of Yale University, Dr. E. O. 

 Ulrich of the U. S. Geological Survey, Dr. C. K. Swartz of 

 Johns Hopkins University, and others for assistance. He is 

 further indebted to the Director of the Maryland G-eological 

 Survey for the privilege of publishing this article. 



Before turning to the present discussion of the Meso-Silurian 

 in Maryland, let us make a brief historical review of what 

 has already been done in this area and what have been and are 

 the views held concerning it. 



Historical Review. — Nearly fifty years ago Philip Tyson, 

 the state agricultural chemist of Maryland, published * the 

 first report of importance dealing with the geology of western 

 Maryland. He touched but briefly upon the formations under 

 consideration, using terms, " the Clinton" for the pre-Rochester 

 Meso-Silurian' and "the Onondaga" for the remainder of the 

 Meso-Silurian and the Cayugan. In 1874 Prof. James Hall 

 of New York, who had worked in Maryland, especially in the 

 Lower Helderberg, did not recognize the presence of Niagara. 

 It appears that he later did, as he cites Spirifer crispus and 

 Homeospira apriniformis from the "Niagara" of Maryland. 



In 1893 a preliminary geological map f of the state showed 

 the whole Meso-Silurian deposits under the name " Rockwood." 

 James D. Dana;}; in 1895 recognized in Pennsylvania, immedi- 

 ately north of Maryland, a commingling of Clinton and Niag- 

 ara fossils in the upper Clinton beds, and states that there 

 frequently occur some distance above the top Clinton iron-ore, 

 a succession of thin limestones which in many places contain 

 Niagara fossils. 



The author of the Piedmont Folio § discussed a part of the 

 Maryland area, using the terms Pockwood-(Clinton or pre- 

 Rochester Meso-Silurian) and Lewiston (later Meso-Silurian, 

 Cayugan and Lower Helderberg). There is here a preliminary 

 discussion of the two formations as Rockwood and the lower 

 part of the Lewiston. 



The first detailed lithological study, however, of the Meso- 



* Geological Map and Eeport, 1861. 



f Map to accompany "Maryland: Its Resources, Industries, and Insti- 

 tutions." G. H. Williams and W. B. Clark. 

 X Manual, 4th edition, 1895. 

 § Geol. Survey Atlas, Folio No. 28, 1896. 



