The Galena and Maqnoketa Series. — Sardeson. 381 
kinds of Trenton that already have been entered on tlie list 
of synonymous terms for formations in the Wisconsin, Illi- 
nois, Iowa and Minnesota area of Ordovician. C. D. Walcott 
has correlated in like manner the Galena formation with the 
Utica slate horizon, and not improb':ibly some will still prefer 
the name Utica instead of Trenton for the Galena formation. 
N. H. Winchell has presented in detail his argument in favor 
of the name Trenton, and the reader is respectfully referred 
to Winchell's discussion for facts bearing upon the question.* 
I have some reasons for believing that Winchell and Walcott 
in their arguments upon this question agree more nearly than 
at first would appear, and that both may be at the same time 
near the truth. Walcott must have included in his Galena 
limestone that which has been heretofore called Galena in Il- 
linois, Wisconsin, and around Dubuque, Iowa, and as I have 
pointed out in my former paper, the Galena formation thus 
defined includes not only the Galena but also, at the top, the 
Triplecia bed which contaiiis chiefly Maquoketa (Hudson) 
fossils. Walcott probably found his evidence of Utica fauna 
in fossils that are really from this bed only. Winchell, at the 
time his discussion was written, did. on the contrar}^ that 
which all other geologists had done in Minnesota at that time, 
viz, considered the Triplecia bed as not Galena. Winchell 
and Ulrich {loc. cit., p. cxv) still tabulate the Triplecia ul- 
richi W. and S., and the associated fossils that are peculiar to 
this Triplecia bed or Transition formation, with the Maquo- 
keta (Utica) formation's fauna. They are not clear, however, 
in the definition of this bedf stratigraphically, though, 1 
think they will concur in placing the Triplecia bed apart from 
the Galena (Trenton) formation, and in the Maquoketa (Uti- 
ca). It is not improbable that the argument presented by 
Walcott and that by Winchell may be harmonized, and no 
conflicting nomenclature result from it, but evidently so long 
as the nomenclature of the Trenton (Galena) and Hudson 
(Maquoketa) series depends upon correlation with distant 
equivalents, difference of opinion in the minds of geologists 
will cause repeated shifting of names and confusion in this 
area. Moreover, difference of opinion cannot be excluded. 
*See American Geologist, vol. xv, p. 33-39. (1895). 
tSee loc. cit., p. civ, 1. 29. et seq. 
