340 C. D. WALCOTT — THE I'KKM "HUDSON RIVEB GROUP." 



New York and tlie Mississippi valley, He then proposed to drop the term 

 Hudson River group. In explaining this note he Bays:* 



•• In the nomenclature proposed by the geologists of the State of New York for 



the Beveral formations within the region of country explored by them the term Hud- 



l; ■ • group was applied to a series of shales and argillaceous sandstones, with 



intercalated beds of limestone, which exist in great force along the Hudson river 



valley for a hundred miles above the Highlands. 



••In this disturbed region the order of sequence does not appear to have been fully 

 made out; but a- the western extension of the Hudson-valley rocks along the Mo- 

 hawk valley had been (as then supposed) traced to a junction with rocks known in 

 the Annual Reports of the State Geologists by the names of I ate, Fra 



slate, shales and sandstones of Pulaski, and Lorraine shales, which rocks were known 

 to rest <m the Trenton limestone group, the single term of Hudson River group was 

 proposed to embrace the entire series. In this the expressed object was to give the 

 name from the locality which ofl'ered the most complete and extensive exhibition of 

 the strata composing the group." 



He stated that he was satisfied from the geologic relations of the great 

 mass of these slaty rocks and Prom their contained organic remains that they 

 were of older date, and that the fossils of newer age occurring in differenl 

 localities have not been regarded as characterizing the formation ; that the 

 great mass of the Hudson River rocks in the typical localities arc older than 

 the Lorraine -hale-, the shales and sandstones of Pulaski, etc. ; and that the 

 term Hudson River group cannot properly be extended to these rocks, which, 

 on the wesl Bide of the Hudson river, are separated from the Hudson River 

 group proper by a fault not yet fully ascertained. He added : 



"There can be no propriety in transferring the name Hudson River group from it- 



typical locality and applying it to rocks which we now know to 1 f younger age, 



and which, when the sequence is complete, are separated from the Hudson River 

 rocks by a great limestone formation. 



■ I have therefore dropped the term Hudson River group in its application to the 

 rocks of Wisconsin, which are of the age of the Lorraine shales of New Fork and 

 the Blue limestone group of Ohio. - ' 



Fifteen years after publishing the note in the ( S-eology of Wisconsin in L862 . 

 Professor Hall reviewed the evidence on which his conclusions were based 

 and decided that he had been in error in dropping the term Hudson River 

 group. He Baysl thai be accepted the determination made by the Geologi- 

 cal Survey of Canada regarding the extension of the older rocks marked 

 by the preseuce of a primordial fauna into the Hudson and Champlain val- 

 leys; also, al the time, the suggestion thai the few fossils of the Trenton 

 fauna of the Hudson River shales were contained in some outliers of insig- 



R ivi t Group in \ne fom- 



- i , rol. -'■, 1877, pp. 



