THE LOWER DEVONIAN DEPOSITS 

 OF MARYLAND 



CHARLES SCHUCHERT, C. K. SWARTZ, T. POOLE MAYNARD, AND R. 

 ROWE 



INTEODUCTORY ' 



The typical development of the Silurian System was first made out in 

 Wales and in the adjoining counties of England and described by Murchi- 

 son. Here the prolific marine faunas of the shales and limestones gradu- 

 ally disappear in the upper series — the Ludlow. The strata by degrees 

 take on a red color and seem to pass without break from brackish-water 

 deposits into fluviatile sandstones and conglomerates. This great series 

 of continental sediments is unfossiliferous, except for the eurypterid re- 

 mains of Pterygotus, the " seraphim "' of the quarrymen, and the varied 

 array of fresh-water fishes. This series of coarse fragmentals is the Old 

 Red Sandstone and is more than 10,000 feet in thickness. In the typical 

 area of the Silurian system, therefore, there is no final marine fauna. 

 The original Devonian also lacks a definite marine base. These conditions 

 are further complicated by the fact that nowhere in western Europe is 

 there a fairly complete succession of Silurian and Lower Devonian strata 

 yielding abundant marine faunas. There is, however, a splendid section, 

 rich in the fossils of these two systems in the Bohemian region, all of 

 which Barrande referred to the Silurian. The dividing line between these 

 two systems is there definitely drawn at the base of the Koniepriisian, a 



' Contributed by Charles Schuchert who states that all the faunal work was 

 accomplished previous to 1904 while Assistant Curator in the U. S. National 

 Museum, and all the writing was completed before the appearance of Clarke's 

 Early Devonic History of New York and Eastern North America. All the new 

 forms, however, have been reconsidered in order that no synonyms may appear 

 In this volume. 



