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NEW YORK STATE MUSEUM 



ployed by the original state geologists in any other form and it is 

 evident that the significance here of the term group is its refer- 

 ence to the variability of the strata in the typical Madison county 

 sections where they are sandstones, arenaceous and argillaceous 

 shales, not a composition of defined lithologic units. In other 

 words the term is used with the same breadth of meaning as other 

 unit terms of the series and not as the word was subsequently em- 

 ployed in the final reports of the geologists nor in the widely dif- 

 ferent sense made use of by Dana and generally current. The 

 division was clearly defined and its place in the series is precisely 

 that ascribed to the Ludlowville shales in the Cayuga lake section 

 as was defined by Hall in 1889. Ludlowville was not altogether 

 well chosen as exemplifying the latter division, for the Tully lime- 

 stone is present in the village and the Moscow shales beneath ; one 

 must go afield to find the true Ludlowville strata, but it is evi- 

 dent that Professor Hall's conviction at that early day that 

 these were the representatives of the Ludlow shales of Eng- 

 land, influenced his choice of name. We would reject neither 

 name in favor of the other. Each expresses essentially the 

 same interval but a differing series of sediments and some 

 marked distinction in fauna. Each will be found to have a 

 definite meridional value. Hence further west and in the area 

 here under consideration we find still other differences ex- 

 pressed in this interval both lithologic and faunal and are 

 constrained to express these by the terms employed above. 



The Canandaigua shale is constituted of soft, dark bluish 

 and gray calcareous shales with impure limestone beds at the 

 bottom, and irregularly nodular calcareous beds abounding in 

 corals toward the middle of the formation. This is a highly 

 fossiliferous mass and its distinction from the beds beneath 

 lies not alone in the nature of its lithologic character, but 

 essentially in the abrupt manifestation of the highly profuse 

 and typical Hamilton fauna. The Skaneateles and Cardiff shales 

 have been regarded as a kind of transition deposit from 

 the typical bituminous Marcellus shales indicating the 

 gradual approach and encroachment of uormal Hamilton 



