Review of Recent Geological LitenitHre. 347 
try and and ascertain the true biologic interpretation of the characters 
observed, and not rest satisfied until the relations existing between 
classes and orders and genera are established on a reasonably natural 
basis. There are no hard and fast lines in the realm of fossil organic 
remains, no more than in recent biological researches. 
We almost go so far as to say that in studying any extensive series 
of fossil remains, even from the old palaeozoic formations, we cannot 
truly state that either a genus and a sjtecies is a term that can be defi- 
nitely and distinctly characterised so as to include known or afterwards- 
to-be discovered forms. 
Nevertheless, it is quite convenient and reasonable to create genera 
and species. A careful study of the pala^ontologic characters of a 
group of organisms from a definite series of sediments will be most help- 
ful in future correlations of strata in different parts of the continent, 
serve to throw light upon the origin and cradle of certain types, and on 
their subsequent migrations and vicissitudes due to the differences of 
marine conditions in those early times. 
The board of regents of the University of Minnesota and the state 
geologist and his staff deserve congratulations on the completion of vol. 
Ill, part II of their final report upon the geology of Minnesota. Vol. iii, 
pt. I contained, besides a "historical sketch of investigations of the 
Lower Silurian in the Upper Mississippi Valley," a series of chapters on 
"Cretaceous fossil plants from Minnesota," by Leo Le'squereux; ''The 
microscopical fauna of the Cretaceous in Minnesota," etc., by Wood- 
ward and Thomas; "Notes on other Cretaceous fossils in Minnesota,'' 
N. H. Winchell; "Sponges, graptolitos and corals from the Lower Silu- 
rian in Minnesota," N. H. Winchell and Charles Schuchert; "On Lower 
Silurian Bryozoa of Minnesota," E. O. Ulrich; "The Lower Silurian 
Braehiopoda of Minnesota," N. H. Winchell and Charles Schuchert, 
the whole forming a handsoQie volume of 474 pages, illustrated by forty- 
one plates and thirty-four figures, issued July, 1895. 
This volume (iii, pt. ii, issued Feb. 2d, 1897) opens with an introduc- 
tion by N. H. Winchell and E. O. Ulrich on "The Lower Silurian de- 
posits of the Upper Mississippi Province," giving the stratigraphic and 
geographic distribution of the fossils. This is followed by a chapter on 
"The Lower Silurian Lamellibranchiata of Minnesota," byE. O. Ulrich; 
"The Lower Silurian Ostraeoda of Minne-^ota," by E. O. Ulrich: then 
comes two chapters by Prof. J. M. Clarke on "The Lower Silurian 
Trilobites of Minnesota," and on "The Lower Silurian Cephalopoda of 
Minnei^ota," closing with Chapter X, on "The Lower Silurian Gastro- 
poda of Minnesota," by E. O. Ulrich and W. H. Scofield. 
The editors record with sadness the loss of the last mentioned author 
who died during the preparation of this volume. His death will not 
only he a loss to Minnesota, but to geological science. 
In reviewing the palaeontology of this volume I will deal with each 
chapter separately. Part ii of vol. in, opens with Chapter VI, — ''The 
Lower Silurian Lainellibranchiatd of Minnesota.'''' By E. O. Ulrich, 
pp. 475-628. In this chapter we note that the genus AinhonychiaWaW, 
