22 NEW YORK STATE MUSEUM 



The Clinton formation was first called, by Vanuxem, the 

 Protean group, on account of the variable character of its sedi- 

 ments and their colors. AVhen, soon after, the geographic term 

 Clinton was substituted for the formation, it was based on the 

 rock section referred to at Clinton village, its lower limit being 

 recognized as bounded by the Medina sandstone there present, 

 but its upper limit being undefined, or in other words, the entire 

 section there exposed above the Medina formation being left as 

 the exponent of the Clinton formation. In the Genesee valley 

 the Clinton term was also recognized and used contempora- 

 neously by Hall. There the formation is much more advantage- 

 ously and completely expressed, and over it lies Avithout inter- 

 ruption a bed of gray shale which was separately designated by 

 Hall as the Rochester shale. 



Our knowledge of the fauna of the Clinton unit, as well as 

 of the Rochester shale, has been essentially derived from the 

 Genesee section. With the progress of knowledge it is satis- 

 factorily determined that at the Clinton section at Clinton is 

 a weak development of the Rochester shale and this was included 

 by inference in Vanuxem 's definition of the Clinton formation. 



In actual date of establishment the term Rochester shale is 

 older than Clinton, but only the work of later years has shown 

 the presence of the earlier named formation in the '' type " 

 section of the latter. The question has, from these acknowledged 

 conditions, arisen in this form : Shall the Clinton formation be 

 made to include the deposits and fauna of the Rochester shale? 



In New York we have felt disposed to hold the view that the 

 early geologists, of course totally unaware of the sharp and pre- 

 cise requirements of an advanced knowledge, employed forma- 

 tional terms with some degree of elasticity, even of laxity, and 

 in the particular case in hand, that the rock succession in the 

 Genesee valley is a truer demonstration of actual relationships 

 and its early denominations a more faithful expression of suc- 

 cessive geological events than either section or names in the 

 Clinton section. It seems to us doubtful whether ancient and 

 loosely defined names can wisely be resuscitated, in defiance of 

 advances in knowledge, or whether such attempts at resuscita- 

 tion are not virtually new definitions, thus lacking wholly the 

 merit claimed for their age. 



The stratigraphic contrast in these two sections is very pro- 

 nounced. In the Rochester or Genesee river section the Clinton 



