XX11 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 Eichardson. 



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, ivith an 

 appendix on the physical geography of North America, by SIK 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. POSTER and J. D. WHITNEY, 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 elastics, 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. POSTER and 

 J. D. WHITNEY, 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- 



