XXil THE PALEONTOLOGY OF MINNESOTA. 
the Cliff) limestone of the Dubuque district, and some found in the Blue limestone of the 
Ohio valley. all being of Silurian type (p. 30). 
Sir John Richardson. 
1848. Arctic searching expedition: a journal of a boat voyage through Rupert's land and 
the Arctic sea, in search of the discovery ships under command of Sir John Franklin, with an 
appendix on the physical geography of North America, by Str JOHN RICHARDSON, C. B., F. 
R. S. 8vo. 1852. Harper Brothers, New York. 
Dr. Richardson in this journey obtained information which authorized him to refer the 
limestones on the western shores of lake Winnipeg to the Silurian, ‘‘chiefly birds eye 
limestone.” 
Foster and Whitney. 
1850. Report on the geology and topography of a portion of the Lake Superior land district 
in the state of Michigan, by J. W. Foster and J. D. Wuitney, U.S. Geologists; in two 
parts.—Pt. I, Copper lands; 31st Congress, 1st session, House doc. 69; Washington, 1850; 
pp. 1-224. 
On pages 117 to 119 the ‘‘Compact, or Lower Magnesian Limestone” is described; all 
the clastics, above the Potsdam, found just west of Keweenaw bay are included under this 
head. A small number of fossils were collected and submitted to professor James Hall, 
who says: ‘‘The evidence from the whole together goes to prove that the rocks from 
which they were obtained belong to the older Silurian period.” Concerning the fossils, all 
of which were imperfectly preserved, the author concludes: 
“From all of the facts, these fossils may be regarded as belonging to the earlier types of organic 
life. From the limited scale on which these deposites are developed, and the imperfect character of the 
organic remains, it is impossible to fix their precise equivalents in the New York classification. The 
sandstones and limestones which we have described may be regarded as the equivalents of the Potsdam 
and Calciferous sandstones, the Chazy, Birdseye, and Black River limestones, and perhaps of the Trenton 
and even the Hudson River groups.” 
This rock appears in outcrop ‘‘ west of Keweenaw bay,” near the quarter-post 
between sections 13 and 14, township 51, range 35, also a little west of the line between 
sections 23 and 24, extending for a little more than a mile, forming a high cliff running 
south. 
Foster and Whitney. 
1851. Report on the geology of the Lake Superior land district, by J. W. FOSTER and 
J. D. Wurtney, U. S. Geologists; Pt. II. The iron region, together with the general 
geology; Special session, March, 1851, Senate doc. 4; Washington, 1851; pp. 1-406. 
This report is accompanied by several sections and a geological map of the shores of 
lake Superior and the upper peninsula of Michigan. The map shows an area of Trenton 
limestone (including Chazy, Birdseye and Black River limestones) along the west shore of 
Green bay. On the east shore of this bay are rocks of the Hudson River group, and from 
here these two formations (Trenton and Hudson River) extend in a narrow belt northeast 
and east through the centre of the peninsula to its eastern end, the latter group lying 
immediately south of the former. The Chazy, Birdseye, Black River and Trenton lime- 
