686 The American Naturalist. [August, 
problem of even greater significance awaits the labors of the Survey. 
This is the discrimination of the Cambrian and Ordovician beds of the 
eastern border of the mountains. The Calciferous and Trenton lime- 
stones both exist in this series, but they are stillincluded in one forma- 
tion by the present survey, as they were by the first survey, as No. II. 
Walcott has already made some progress in this direction, and it is 
certain that many important results will be obtained by further re- 
search. 
s Eos " Sem 
Mia: ee A m e CHEER d 
