446 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



2. The Niagara group lies discordantly on the Hudson-River 

 group in Gaspe, the Eastern townships, and Vermont, (p. 178.) 



3. " Undulated Matinal rocks support horizontal Niagara or 

 Scalent strata, with a lapse of two intermediate formations for 

 some distance from the Hudson, westward along the base of the 

 Helderberg range." (p. 178.) 



4. Unconformity extends west of the River Hudson as far as the 

 Oneida Lake, a distance of about 120 miles, with and without in- 

 terruption of sequence in the strata, (p. 178.) 



5. The Levant beds (Medina Sandstone and Clinton Rocks) evi- 

 dence this crust-movement in every feature of their composition. 

 The lower bed is a conglomerate of Cambrian pebbles and sand, 

 (p. 179.) 



6. "Over half the width of the [Western] Continent there exists, 

 notwithstanding an almost absolute horizontality and parallelism of 

 the two sets of strata, or the lower and middle palaeozoic series, a 

 true discontinuity in the sequence of the formations. In New 

 York there is a conformable interrupted sequence* from the Hud- 

 son to Oneida County : from Oneida to Lake Ontario, the Levant 

 Conglomerate or Lowest Silurian stratum enters the gap and makes 

 the sequence complete." 



7. The Professor goes on to say that there is a similar and con- 

 temporaneous break at Cincinnati in Ohio. The lower palaeozoic 

 strata coming to day there, the Niagara Limestone rests upon the 

 Hudson-River group direct, there being no Medina Sandstone there, 

 and little of the Clinton rock. (p. 180.) This break is repeated in 

 a still more striking manner in Tennessee, as well as in Southern 

 Wisconsin and Eastern Missouri. In this last region, and further 

 west, " there is a chain of broad anticlinals, exposing ancient plu- 

 tonic and gneissic rocks, but chiefly the older palaeozoic strata near 

 their axes. Around every one of these, either the middle, that is 

 Silurian and Devonian, or upper, namely Carboniferous deposits, 

 rest in discordant superposition (with or without parallelism) upon 

 the Primal, Auroral, and Matinal members [Potsdam, Chazy, and 

 Hudson-River groups] of the older palaeozoic division." (p. 180.) 



The PalcBontoloyical Break. — This is more remarkable than the 

 physical, according to Mr. Rogers (p. 181), who states that only 

 three dilapidated fossils escape from below the break into the strata 

 above, namely Bellerophon trilobatus, Delthyris Lynx, Leptcena al- 

 ternata, with a few dubious fragments of other fossils which appear 

 to be forms belonging to Lower Silurian strata (p. 183). "This 

 horizon of the upper limit of the Matinal rocks is incontestably the 

 sharpest, palaeontologically, within the whole palaeontological system 



* " One set of strata may rest immediately on another with perfect parallelism, 

 and yet their plane of contact represent a long interval of time and a total change 

 of sedimentary conditions and of the physical geography ; for certain heds, or 

 even whole formations interposed between them in other districts, may be alto- 

 gether absent. This relationship is entitled a conformable interrupted sequence. 

 It proves not merely a lift of the watery floor into dry land, and its subsequent 

 re-immersion, but a movement unaccompanied by any tilting or undulation of the 

 lower deposit." (Loc. cit. p. 178.) 



