126 TWENTY-SEVENTH EEPOET ON THE STATE MUSEUM. 



the north-west part of that State the formation has been dis- 

 tinctly recognized by Professor Cook. The same has been 

 fully described as the "Limestone formation, No. VI," in the 

 Geological survey of Pennsylvania, in which State it appears 

 in numerous outcrops, and extends thence through the western 

 part of Maryland and through Virginia, along the Appala- 

 chian range into Tennessee. 



Nowhere*throughout this extent of country, as far as Vir- 

 ginia, has any one shown, or attempted to show, the mingling 

 of Lower Helderberg and Niagara forms among the fossils. 

 In the large collections which I possess from Maryland and 

 Virginia, I have never observed the least evidence of such 

 mingling ; and in Maryland and the adjacent parts of 

 Virginia (I can speak from personal observation) the forma- 

 tion is as well defined, physically, as in any part of New 

 York. 



Let us now look to the north-east, where the Geological sur- 

 vey of Canada has traced the Lower Helderberg formation 

 from Montreal to Gaspe. Having examined large collections 

 of these fossils from the Gaspe region, and others from near 

 Montreal, I have never seen the least indication of a ming- 

 ling of any other forms with those characteristic of the Lower 

 Helderberg. 



We have now traced this formation from the forty- third 

 parallel in the State of New York to about the thirty-fifth 

 parallel of latitude in Tennessee, and over the greater part of 

 this extent we have no knowledge of a mingling of the fos- 

 sils of the two groups or formations. Again, from the vicin- 

 ity of Montreal to Gaspe, a distance of some seven hundred 

 miles, the formation, wherever known, carries its characteristic 

 fossils. 



This group is likewise recognized in the State of Maine, where 

 it is characterized by numerous well-known fossils ; and it is 

 not improbable that it may be equally so in the eastern town- 

 ships of Canada and in the belt of limestones extending through 

 Vermont to the northern part of Massachusetts. 



Having thus hastily sketched the ground occupied by these 

 two groups of strata, we may now consider their relations 

 to each other, and the evidence of the mingling of the fossils 

 which would render it necessary to relieve the nomenclature 



