180 The American Geologist. March, i8'j7 
Since thig paper was written, the 16th Annual Report of the 
United States Geological Survey has appeared, containing 
Van Hise's important discussion of the principles of Pre- 
Cambrian geology. We are pleased to see (p. 687) that he 
holds very strongly to the essential continuity of fusion and 
solution at great depths in the earth, and finds in this coop- 
eration of aqueous and igneous agencies the best explanation 
of the main part at least of the pegmatites, although hold- 
ing with Brogger that they are, in part, of normal igneous 
origin. 
THE GALENA AND MAQUOKETA SERIES. 
By F. W. Sardeson, Minneapolis, Minnesota. 
Part IV. 
In parts one and two of this paper a revision of the Ga- 
lena and Maquoketa series has been discussed and a classifi- 
cation has been outlined in emended form. The two series are 
divided primarily into fourteen beds and secondarily into live 
formations each of which includes one or more of the beds. 
In order to illustrate more fully the paleontological evidence 
upon which the classification is largely based, parts three and 
four of the paper are devoted to the discussion of that sub- 
ject. Part three is a digression comprising a paleontological 
study of the very important Galena (Trenton) and Maquo- 
keta (Hudson) fossils known collectively as Orthis testudiiKiria 
Dal. Two similar groups will be added here in order that 
they may be united in the subsequent discussion, but it will 
not be necessary for the present, to enter so fully into the 
paleontological discription of these as of that one. Such 
wide digressions if repeated might result in making the major 
title of my paper non-representative of its major content, 
and cause the final and premeditated discussion to be crowded 
into a mere footnote. The discussion of Orthis testndiuaria 
itself in part three is taken from a larger unpublished work 
of mine, and adapted to the present needs because it repre- 
sents one of the most necessary stages of paleontologico- 
geological study of the Galena and Maquoketa series. The 
same spirit is intended to pervade the study of O. testudi- 
iKiria and the two other groups of related Brachiopoda that 
are chosen for comparison with it, and it will be sufficient to 
