INVES ODUCTION-LO VO. ih PART 
HISTORICAL SKETCH OF INVESTIGA- 
HON: OF TEE LOWER SILURIAN 
NSE eae SSiSsLe Pa: 
WAIGHY. 
BY N. H. WINCHELL AND E. O. ULRICH. 
The paleontology of the Lower Silurian, as exemplified in the rocks of Minnesota and 
adjoining states, has been strangely overlooked and neglected. As a geological horizon 
the rocks of the Lower Silurian everywhere bear important relations to those which 
followed and to those which preceded them. The profuse fauna with which they are 
characterized is the first, after the Taconic, which displays its zoological affinities with 
distinctness, and at the same time with a sufficient number of well-preserved specimens 
to indicate the nature of the life which filled those Paleozoic seas. As a descendant from 
the Primordial fauna it manifests so great variations, and so great a number of species, 
that it holds an independent rank in the paleontological record equal in importance to 
any which followed, and superior to any that preceded. As the second great faunal epoch 
the Lower Silurian gives the first affirmative stamp to the idea of the evolution of species. 
The variation of forms which began in Primordial time, once established by a careful 
study of the ‘‘second fauna,” the elucidation of all succeeding faunas by the application 
of the same research guided by the same laws, would follow as a necessary logical result. 
Too often this natural sequence has not been followed by paleontologists, but higher 
stages of variation, separated perhaps by many steps from the original forms, have been 
chosen for study and illustration. This has resulted sometimes in wrong conceptions 
concerning the sequence of change, or the manner of development from the comprehensive 
forms to those that are more specialized. To some species have been assigned what have 
proved to be unnatural progenitors, and imaginary progenitors have been assumed for 
others, while many apparently had no former ancestral species to which they could be 
traced. The examination of the intermediate links has shown where these errors have 
been committed. Such has been the function of the Lower Silurian fauna, as illustrated 
in numerous instances in the preparation of this volume, 
