REPORT OF THE STATE PALEONTOLOGIST 1901 427 



report I have given further detail as to the results of field work 

 in this area with special reference to locating the formational 

 contact lines, and it may here be stated briefly, that the out- 

 come of this work has been to correct in some important par- 

 ticulars these lines as heretofore registered on our geologic 

 maps. Because of the scarcity of outcrops, however, the course 

 of these contacts may always remain more or less conjectural. 

 Stratigraphic and paleohtologic relations of Potsdam sandstone of 

 the Lake Champlain basin to overlying limestones. During some 

 years past Mr Gilbert van Ingen, special field assistant, has 

 been concerned with the study of the fauna of the lower lime- 

 stones of our rock series, specially those of the Beekmantown 

 and the Chazy horizons as developed in the basin of Lake Cham- 

 plain. These formations have furnished a large amount of new 

 evidence as to the constitution of the faunas of the times they 

 represent. Having acquired special familiarity with the faunas 

 of these rocks, Mr van Ingen has at my request undertaken 

 during the last season to study the relations which they bear 

 to the underlying Potsdam sandstone, and to ascertain in how 

 far the passage from the latter upward into the former is 

 gradual and what evidence the fossils afford in regard to the 

 transition of the earlier fauna to the later. The ultimate pur- 

 pose of this inquiry is to determine to what degree the fauna 

 of this ancient Potsdam period bears characters which may 

 fix its age as Cambric. Historically this well known formation 

 is the basal member of the " New York series of formations ^' 

 as enunciated by the four geologists of the early survey. Dr 

 Ebenezer Emmons, in defending, against the convictions of his 

 colleagues, the existence of a series of still older fossiliferous 

 sediments (the Taconic system) did not propose to embrace with 

 them the Potsdam sandstone, a formation of which he also was 

 the demonstrator. The Potsdam sandstone is furthermore 

 clearly a- shallow water or littoral deposit accumulated along 

 the shelving shores of the most ancient crystalline continent, 

 and is the oldest deposit of this character of which we have 

 anv knowledoje in our rock series. Farther out at sea in the 



