114 Barrande, Logan and Hall 



After the descriptions had been printed and a few copies distri- 

 buted, I learned that Sir William Logan was at that time actually 

 investigating the rocks of that part of Vermont. Desiring to 

 know the results of his latest researches in regard to the strati- 

 graphical relations of these rocks, I withheld the final publica- 

 tion till the meeting of the American Association for the Advan- 

 cement of Science, in Springfield, and there showed to Sir William 

 my descriptions as they now stand in the report, and I then re- 

 ceived his authority for the addition of the note which was ap- 

 pended. 



This in a few words is a simple history of the matter relating 

 to the publication of these species. I made no remarks or com- 

 parisons with the primordial fauna of Barrande in Bohemia, know- 

 ing that these features would be at once recognized by every pal- 

 aeontologist ; while their reference to the genus Olenus showed 

 my appreciation of the nature of the fossils. 



T received a copy of the communication of Mr. Barrande, from 

 Sir William Logan in September, a few days before setting out 

 for my field duties in Wisconsin. Since my return to Albany, 

 constant and pressing occupation has left me no time to consider 

 a reply to a question of so much importance. 



Later discoveries in the limestones associated with the shales 

 at Quebec leave no longer a doubt, if any could have been enter- 

 tained before, that the shales of Georgia, Vermont, are in the 

 same relative position ; and we must regard these three trilobites 

 as belonging to the same fauna with the species enumerated by 

 Sir William Logan as occurring in the Quebec group. Left to 

 palseontological evidence alone, there could never have been a 

 question of the relations of these trilobites, which would at once 

 have been refeiTcd to the primordial types of Barrande. 



Sir William Logan yields to the palgeontological evidence, and 

 says, " there must be a break.^^ He gives up the evidence of 

 structural sequence which he had before investigated and con- 

 sidered conclusire ; and having heretofore relied upon the opin- 

 ion of the distinguished geologist of Canada in regard to a region 

 of country to which ray «wn examinations have not extended, I 

 have nothing left me but to go back to the position sustained by 

 palseontological evidence. Let us for a moment examine this 

 palaeontological evidence. 



The identifications of the fosssils of the Quebec group certainly 

 show a remarkable agreement between the trilobites of this group 



