746 L. D. BL'RLIXG CAMBRO-OKDOVICIAN NEAR MOUNT ROBSON 



"In the description of the species Pcecleumias rodsonensis you give the 

 horizon as Mahto. Walcott in his description of this fauna gives it thus also, 

 but in his next paper (July 24) he gives the fauna as occurring in the Hota. 

 I called his attention to this difference and he says the correct formation is 

 the Hota." 



(§ 32e.) As we have showii (§§ 30c, d, g, and 32c), the '^new Lower 

 Cambrian subfauna'' of Walcott occurs not in the ^'Hota/' but in the 

 Mahto or the "Tah/' In the absence of any recognizable break, the line 

 between these two formations has now been drawn (§86) so as to include 

 in the overhang Mahto only the dominantly arenaceous series and so as 

 to transfer to the underlying '^'Tah^' the essentially calcareous series. 

 Such a separation places the "new Lower Cambrian subfauna" 550 feet 

 below the top of the "Tah" (Mural limestone) formation. 



The differences between the interpretations of Mr. Walcott and myself 

 are in no way dependent on the drawing of the line betw^een the "Tah" 

 and the Mahto. He said, and repeats through Mr. Eesser, that the "new 

 Lower Cambrian subfauna" came from the "Hota," a formation over- 

 lying the Mahto. We have visited the type locality and have found the 

 fauna under discussion in the "'Tah,'' a formation underlying the Mahto. 



(§ 32/.) The Mural limestone formation is one of exceptional interest; 

 and w^hile all of the fossils secured by Walcott, as well as the specimens 

 described b}' the writer, were secured from drift blocks in the lateral 

 moraine of the Mural Glacier, an abundant fauna has now been secured 

 from the formation itself. In addition to being very fossiliferous in its 

 locality above the Mural Glacier on Munim Peak, the i\[ural limestone 

 formation is tliere shown in observable relations with its over- and under- 

 lying formations. The underlying sandstones (not certainly to be corre- 

 lated with the MciSTaughton sandstones of Walcott) are here over 400 

 feet thick. 



(§ 32_g.) Our main reasons for making the change from "Tah'^ to 

 Mural are the failure of the Geographic Board to accept the name, the 

 remoteness of the mountain, the absence there of observable relations to 

 the other formations and of fossils, and the confusion of the "Tah" and 

 the "Hota," stratigraphically, lithologically, and paleontologically. 



MC NAUGHTOX SANDSTONES (§3.3) 



(§ 33a.) The McNaughton sandstones are described by Walcott from 

 the McNaughton Mountains, some 20 miles distant from the locality in 

 which the other formations were identified. They are there given an 

 estimated thickness of 500 feet and are described as unfossiliferous. The 



