378 BARRANDE'S VIEWS. 



most characteristic forms of the Primordial fauna, and giving them names the most significant of this first 

 creation, he thinks it his duty to teach us that these three trilobites belong to a horizon superior to that on 

 which the second fauna is extinguished. 



" In effect, according to the text of J. Hall, the three trilobites in question were found near the town of 

 Georgia, Vermont, in schists which are superior to the true Hudson River grpup. In his work J. Hall 

 does not go beyond indicating the horizon of certain fossils, and no one would think of asking a guaranty 

 for such indications. But on this occasion the great American paleontologist thinks it necessary to support 

 his stratigraphical determination by another authority, chosen from the most respectable names in geology. 

 The following is the note which terminates his Memoir. 



u i NOTE. In addition to the evidence heretofore possessed regarding the position of the shales contain- 

 ing the trilobites, I have the testimony of Sir W. E. Logan, that the shales of this locality are in the upper 

 part of the Hudson River group, or forming a part of a series of strata which he is inclined to rank as a 

 distinct group, above the Hudson River proper. It would be quite superfluous for me to add one word in 

 support of the opinion of the most able stratigraphical geologist of the American continent.' 



" Now, when a savant like J. Hall thinks himself obliged to invoke testimony to guarantee the exactness 

 of the position of a few fossils, it is clear that the determination of this position is difficult. 



" In order to understand these difficulties I have consulted the maps and documents relating to the State 

 of Vermont, and the country in which the town of Georgia is situated, and, although the library of our 

 Geological Society does not contain all that one could wish on the subject, I recognized easily that Georgia 

 is placed in the region where the order of succession of the deposits is the most obscured by foldings and 

 dislocations; so that the position of the schists in question could not have been determined by the incon- 

 testable evidence of direct superposition. Besides, the physical appearance of these schists is not that of 

 the rocks constituting the typical group of Hudson River. This is verified by the note of J. Hall, for it 

 tells us that Sir W. E. Logan is inclined to make a distinct group of these schists superior to that of the 

 Hudson, and which consequently would crown the whole Lower Silurian division of the continent. 



" For the above reasons, the geological horizon on which the three Oleni of Georgia were found appears 

 to me, at first view, to have been but doubtfully determined, and in complete opposition to paleeontological 

 documents. 



" I do not think, then, that I weaken in the least degree the respect and confidence justly inspired by 

 the labors of the American savants whose names have just been mentioned, when I ask them in the name 

 of science to make new researches and new studies, that may lead to a final and certain solution of this 

 important question. 



" Doubtless thanks to the progress of our knowledge we are now no longer bound by the ancient con- 

 ception of the simultaneous extinction and the total renovation of the faunae. As for myself, in particular, 

 it would not be possible to accuse me of similar views at the moment when I am publishing the explanation 

 of my doctrine of colonies. But you will perceive that the facts which I invoke in support of this doctrine 

 are far from sustaining the reappearance of a fauna after the extinction of the following fauna, which the 

 three trilobites of Georgia would do, if they had really lived after the deposit of the Hudson River group. 



" This reappearance would be still more astonishing, as among the three great Silurian faunae the second 

 fauna occupies the greatest vertical space and is probably the one which enjoyed the longest existence. 

 Thus, to verify such a reappearance, the most incontestable proofs are required, for such a decision would 

 compel the entire re-formation of one of our most important scientific creeds. 



" Yours very truly. 



J. BARRANDE." 



In another letter, dated Paris, 14th August, 1860, M. Barrande says : 



" You will easily perceive the interest and importance of the question, even if it were only raised on 

 account of the three Oleni of Georgia; but it takes in now a much wider field, owing to a letter I have just 

 received from Mr. Billings, official Palaeontologist of the Geological Survey of Canada, who informs me that 

 he has found lately, in the schists and limestones near Quebec, considered as being the prolongation of those 



