THE PALEONTOLOGIC RECORD 589 



imperfections or gaps in the stratigrapliic column. Measured accord- 

 ing to the sections of twenty-five years ago, the number of these gaps is 

 growing greater and greater, yet with the discovery and intercalation 

 of new formations, the aggregate of which at the present day has almost 

 doubled the thickness of Paleozoic rocks in the last decade, manifestly 

 the great breaks are being reduced. It was not so many years ago that 

 the Potsdam sandstone was supposed to be the oldest fossiliferous sedi- 

 mentary rock, yet now we know that many thousands of feet of much 

 more highly fossiliferous strata intervene between this formation and 

 the Azoic, and that other thousands occur above the Potsdam and 

 below the Ordovician as then recognized. 



With the intercalation of new formations and the consequent 

 diminution in the size of the stratigrapliic gaps, it is then probably 

 only a matter of time before the complete faunal succession can be 

 established. The break in stratigraphy at one point will be bridged 

 over in another area, and it is possible that in only a few regions, such 

 as on the borders of the continent, will permanent gaps exist. Faunas 

 are and will be traced from one area to another until in time we shall 

 know their complete geologic history. With these data in hand, the 

 study of their correlation will not only be greatly simplified, but also 

 will not be hampered by time breaks in the record. While imperfect, 

 or possibly irretrievably lost at the dawn, the faunas of succeeding times 

 are ample for all purposes. 



INTERDEPENDENCE OF STRATIGRAPHY AND 



PALEONTOLOGY 



By Dr. W. J. SINCLAIR 



PRINCETON UNIVERSITY 



IN discussing this subject from the view-point of a vertebrate paleon- 

 tologist, I am disposed to lay stress on what I believe ought to be, 

 rather than what has been, the degree of interpendence of these two 

 branches of geology. Vertebrate paleontology has been studied very 

 largely from the morphological and genealogical side, a study of struc- 

 ture, adaptation and the evolution of phyla. Stratigrapliic geology has 

 been invoked only when it became necessary to know the order of super- 

 position of the various horizons, to determine the true evolutionary 

 succession of a phylum or development of an adaptation. 



I have purposely presented this extreme view, not because I believe 

 that such studies may not be classed legitimately as paleontological, but 

 because I wish to emphasize, by contrast, the view-point which we 

 should ever keep before us as paleontologists — the use of our materials 

 as Leitfossilien. The two correlative conceptions of the faunal unit 

 and the zone, a more or less restricted association of animals and the 



