22 The American Geologist. January, iS97 
tions and beds. By tracing each division continuously, we 
have a means for determining the value of each series and 
each formation, and for reducing them to uniformity. Thus 
it is easily proven that the basal demarcation of the Galena 
series is correct and uniform throughout, as heretofore known, 
and, indeed, the same is unmistakable because marked by the 
striking contact between St. Peter sandstone and the Butf 
limestone hed. So, likewise, the top of the Maquoketa series, 
which is followed by the Niagara limestone, or by the so-called 
Hamilton limestone, is, in either case, marked by a sharp lith- 
ologic and faunal break, which is not easily mistaken. But 
not so wuth the demarcation between the Galena and Maquo- 
keta series, where no one horizon presents an unmistakable 
contrast as compared to any other. 
At Galena, Illinois, the Galena formation is lithologicall^^ as 
it were, extended up into the Maquoketa, for the topmost 
bed, (number .10) contains a fauna belonging most properly 
with that of the Maquoketa (Hudson). Thus, also, at Du- 
buque, Iowa. In northeastern Iowa and in Minnesota, on the 
contrary, this bed has been called Maquoketa shales and mis- 
taken for the true Maquoketa because of its sedimentary and 
faunal aspect. Here, as in Illinois, are found Orthis subqiia- 
drala H., 0. kankakensis McChes., and varieties (or species) of 
0. testudlnaria Dal., of Plectamhonftes sericea Sow., of Ischa- 
dites and of AscqyJixs, such as belong to the Maquoketa and 
not those of the Galena series. With them are others that 
are common to both the Galena and the Maquoketa series. The 
lithological character of the Galena extends in some places to 
the top of this bed, but faunal characters of the Maquo- 
keta series are found everywhere, down to the base, and hence 
I prefer the latter for the divisional line. 
Mr. White, who first applied the name Maquoketa, intend- 
ed, as he says, to "use the name Maquoketa shales to desig- 
nate that particular epochal subdivision or formation of the 
(Cincinnati)group which alone is found in Iowa."* At the 
type locality, Graf Station, Iowa, there is extant the transi- 
tion bed just mentioned, and two other formations. The, 
transition bed he certainly did not include in the Maquoketa. 
The second part is the one that i.s described by him and by 
*Geology of Iowa, vol. i, p. 181, 1870. 
