INTRODUCTION". IX 



In regard to the nomenclature used for the rocks represented 

 in the foregoing section, as well as respecting some modifications 

 made in the same since the publication of the first volume of 

 this Report, it may be proper to add some remarks. In the 

 first place, it will be observed that we have (with a few excep- 

 tions, to be mentioned farther on), retained the names by 

 which these formations are most generally known. In doing 

 so, however, we have dropped the words "sandstone," '"lime- 

 stone," etc., as parts of these names, and substituted the words 

 "group," "division," or "beds," in those names in part derived 

 from lithological characters. Names of the latter kind, or those 

 suggested by the presence of some particular species or genus 

 of fossils at the localities where rocks were first studied, are, 

 from the instability of such characters, often found extremely 

 inapplicable, when we attempt to trace strata far from the origi- 

 nal localities. For this reason, and their consequent liability 

 to mislead the student, there is a growing disposition amongst 

 the highest authorities in geology to drop the objectionable parts 

 of such names, and retain only those portions of the original 

 names derived from the typical localities. In this connection, 

 we need only refer to such works as Prof. Dana's Manual of 

 Geology, and Sir William Logan's Report on the Progress of 

 the Canadian Geological Survey, published in 1863. 



For the lowest division of the Subcarboniferous series, we 

 have used the name Kinderhook group, provisionally proposed 

 by us, in 1861, for a group of arenaceous and more or less cal- 

 careous strata, at the base of the Subcarboniferous, that had 

 been referred by Prof. Hall, and some others, to the Chemung 

 group of the New York series, very generally regarded as be- 

 longing to the Devonian system. Being unable to identify a 

 single Chemung species amongst all our collections from this 

 horizon, and finding them, as a group, decidedly more nearly 

 allied to Carboniferous forms, as well as, in some instances, 

 undistinguishable from species in the Carboniferous limestones 



2 Noy. 1, 1866 



