20 PREFACE 



the writer had the advantage of association with E. 0. Ulrich and George 

 W. Stose in their studies of the stratigraphy and paleontology of that 

 area. He thus helped to collect the data and became acquainted with the 

 Cambrian and Ordovician faunas and sections which are so well displayed 

 there, but not as well developed in Maryland. 



Dr. Richard C. Williams, while a graduate student at Johns Hopkins 

 University, assisted in the mapping of the Cambrian and Ordovician 

 strata, especially in the Hagerstown area. The Maryland Geological 

 Survey has also had the cooperation of the IT. S. Geological Survey, 

 Mr. George W. Stose of that organization being associated in the field 

 work in the Williamsport quadrangle in the area west of the Martinsburg 

 shale belt. 



The Survey is also indebted to Dr. E. 0. Ulrich of the U. S. Geological 

 Survey for permission to incorporate in this volume a set of his paleo- 

 geographic maps covering the Cambrian and Ordovician formations. 



