326 Lozver Silurian Fauna of Minnesota. 



In Fillmore county the Galena is surmounted by twenty, or 

 more, feet of shales, the Maquoketa. These shales in Minnesota 

 consist of alternating strata of shale and crystalline limestone, 

 and are continuous with the Maquoketa of Iowa. But the fossils 

 consist of numerous specimens of a few species of brachiopoda 

 and bryozoa almost wholly different species from what I was able 

 to find in the Maquoketa near Dubuque, Iowa; yet they are not 

 forms that indicate a difference in the age of the strata exposed 

 near Dubuque, and those exposed in Fillmore county. 



Lastly there is upon the Maquoketa shales from fifty to 

 seventy feet of limestone that is very fossiliferous — O. subquad- 

 rata Hall, 0. testudinaria (three varieties, O. whitHeldi Winchell 

 (O. kankakensis McChesney,) Rhynchonella capax Con., Strep- 

 torhynchus wisconsensis Whitf., etc. The fauna appears to be- 

 long to the Cincinnati group. But this limestone appears to be 

 continuous with that identified in Iowa as belonging to the Niag- 

 ara group, though perhaps only in part. In order to avoid confu- 

 sion in subsequent work, I would propose a new name for this 

 limestone — Wykoif beds — from the town near which the best ex- 

 posure known occurs. 



I have never seen any exposures nor any fossils of the Upper 

 Silurian in Minnesota. The Devonian lies unconformably upon 

 the Wykoff beds. Indeed if the Devonian limestone, as is prob- 

 able, extended much further north than it now does, and in the 

 same manner, it rested unconformably upon the Galena or even 

 the Lower Trenton formations within thirty to fifty miles of its 

 present northern limit. As it now lies there it is much less than 

 fifty feet between the top of the Maquoketa shales, and the 

 base of the Devonian at Spring Valley, while only fifteen miles 

 further south near the boundary of Iowa and Minnesota, at least 

 seventy-five feet of limestone intervenes. 



October 6, i8pi. 



THE RANGE AND DISTRIBUTION OF THE LOWER SILURIAN FAUNA OF 

 MINNESOTA WITH DESCRIPTIONS OF SOME NEW SPECIES. 



F. W Sardeson. 



My first intention was to make out a list of Palaeozoic fossils 

 found in Minnesota, with notes on their distribution and vertical 

 range as revealed by thirty or forty exposures. But during prep- 



