176 G. M. DAWSON— STRUCTURE OF THE SELKIRK RANGE. 



that the very thick Cretaceous formations never extended. It must further 

 be borne in mind that the actual width of 100 miles measured across this 

 folded and fiiulted region represents a zone of very probably double this 

 width of the surface as it was antecedent to the great folding and faulting. 

 In tliis zone the line of maximum sedimentation appears to have moved 

 progressively eastward, or away from the local Archean land, in the later 

 periods. 



DISCUSSION. 



Dr. J. W. Spencer: I desire to again -'^ claim priority for the name 

 Algonkian, on the ground that before its publication I had used the term 

 "Algonquin" to designate an episode in the Quaternary history of the 

 region of the Great Lakes. 



Mr. G. K. Gilbert : While the two names referred to by Dr. Spencer 

 are based on the same root, one has the adjective form and the other the 

 nominal, and confusion is thus avoided. The simultaneous and unobjection- 

 able use' of nouns and adjectives etymologically identical for different ele- 

 ments of geologic classification is illustrated in the case of the "Huron 

 shale " and the " Huronian system," and in that of " Erie clay" or "Erie 

 shale" and the " Erian period " or system. The use of "Erie shale" for a 

 Paleozoic formation conflicts with the use of " Erie clay" for a Pleistocene 

 formation, but neither conflicts with Sir William Dawson's term "Erian." 



*Cf. Bull. Geol. Soc. Am., vol. 1, 1889, p. 2.38, note. 



