NO. 4 CAMBRIAN AND PRE-CAMBRIAN AT HELENA 297 



6. {Rothpletz) That No. i of hi.s section (p. 281 ), the green and 

 gray argillaceous shale, occupies the position of the Spokane shale 

 of Walcott. 



6. {Walcott) The Rothpletz shales No. 1 are the shales above the 

 pre-Cambrian, Helena limestone and beneath the Cambrian Flathead 

 quartzite, and occupy the position of the Marsh shale as it occurs 

 elsewhere. 



7. (Rotliplctc) That the fauna of the Capitol Creek shale No. 5 

 of his section is of Lower Cambrian age ( p. 291 ). 



7. {Walcott) The Rothpletz " Lozver " Cambrian fauna of his 

 shale No. 5 (= Middle Cambrian Park shale of Weed) is the usual 

 Middle Cambrian fauna characteristic of the Park shale on Mount 

 Helena and southeast of the city of Helena (pp. 268, 292). 



8. {Rothpletz) That having found a "Lozver" Cambrian fauna 

 in the shale of Xo. 5 and concluded that this shale was interbedded 

 between 4 and 6 in the pre-Cambrian, Helena limestone of Walcott, 

 it followed that the Helena limestone was of Cambrian age and along 

 with it the conformably subjacent Empire and Spokane shales and 

 presumably all of the Belt formations of Walcott. 



8. {Walcott) The Rothpletz identification of the Middle Cambrian 

 Pilgrim and Meagher limestones on Mount Helena and southeast 

 of the city of Helena as the pre-Cambrian Helena limestone of Wal- 

 cott is incorrect, and further it was the main source of the Rothpletz 

 series of errors in connection with the stratigraphic position and age 

 of the Cambrian and pre-Cambrian formations about the city of 

 Helena. 



9. {Rothpletz) That not having observed an unconformity at 

 Helena beneath the Cambrian as stated by Walcott, such an uncon- 

 formity probably did not exist. 



0. ( JTalcott) The Rothpletz failure to find any evidence of an 

 unconformity at the base of the Cambrian is most natural as he un- 

 knowingly identified the Cambrian limestones as the pre-Cambrian 

 Helena limestone and hence did not recognize and probably did not 

 see at all the Helena limestone which is beneath the unconformity. 



10. {Raihplctz) That in the absence of an unconformity at the 

 base of the Cambrian (at Helena) and the absence of a distinctive pre- 

 Cambrian fauna all of the so-called North American pre-Cambrian 

 sedimentary formations of the Belt series -were probably of Cam- 

 brian age. 



