1S67.] 351 [I'erry. 



margin of the Calciferous. Their relations may be in sonic respecty 

 well observed likewise at Whitehall, New York; so in West Haven, 

 an adjacent township of Vermont; also near the village of Orwell, in 

 the latter State, as remarked by Dr. Emmons. 



These groups of rocks, moreover, are seen to bo unconformable, 

 when looked at paUcontologically. Indeed, there is an almost total 

 break, in the sequence of life, between the two formations. If I mis- 

 take not, no species in Vermont, and only one anywhere else, is yet 

 known to have passed upward from the Potsdam into the Calciferous 

 period. The species referred to, which was described by Mr. Billings, 

 is the Pleurotomaria Canadensis. It is possible, however, if not prob- 

 able, as I understand the matter, that even this species is not of so 

 early an age as sujjposed; that the lowest bed in which it has been 

 .found, may be ultimately referred to the base of the Calciferous; and 

 thus, perhajjs, that it did not, after all, make its appearance until after 

 the Potsdam epoch. But, be this as it may, the interruption, all 

 things considered, is clear beyond a cjuestion. Still this pala;ontolog- 

 ical discordance alone, while it is in itself significant so far as it goes, 

 is not enough; it is only negative. It will have greatly increased 

 force, and be made to stand out in a more striking light, if it can be 

 connected with other and positive testimony. 



And there is additional, evidence of a jjositive kind. It is, as 

 may be remarked, to this effect; a different and an advanced zone of 

 life seems to commence with this higher formation. The characteristic 

 primordial forms disappear almost entirely, if not altogether, with the 

 Potsdam; while a new, and what should be perhaps called the second, 

 great chronological type of existence makes its appearance, as it 

 probably has its dawn, in the Calciferous; and it is easily recognized 

 in the fossil remains of this group of beds. Looked at under the re- 

 lations of time, there is seen to be a marked difference between the 

 two formations ; chronologically speaking, the types of life are clearly 

 not the same; indeed, their distinctive marks are widely unlike.* In 

 case, then, I mistake not the evidence (and I really think I understand 

 it), there is a divergence, if I may so express it, of a distinctive 

 character. And this distinction between the two series of rocks is 

 apparently coming to be more fully recognized every year, as their 



* I am happy to be able to say, that the extensive and careful observations recently 

 made by Professor Marcou, ou the older sedimentary formations, in Vermont and 

 elsewhere, tend to establish the primordial character of the Potsdam Sandstone. 

 And this reminds me that I ought not to omit reference to the several i)ublication8 

 of Mr. Marcou on these rocks, to the pahEontological contributions of Mr. Billings, 

 and to the incomparable papers of M. J. Barrande, Sur la Faiine Primonlialeet 

 le Hystcme Taconiqiie en Amurique, as eminently deserving the study of all who 

 would become acquainted with the literature and bearings of the "Taconic ques- 

 tion." 



