EAELY PALEOZOIC BKYOZOA OP THE BALTIC PROVINCES. 



33 



BLACK KIVEE FOSSILS FROM ISLANDS OF LAKE NIPISSING, ONTARIO. 



Ormoceras tenuifilum Hall. 

 * Eschar opor a subrecta Ulrich. 

 Helopora mucronata Ulrich. 

 Escharopora ? limitaris Ulrich. 

 Rhinidictya mutahilis var. major Ulrich. 

 *Phyllodictya varia Ulrich. 



*Batostoma winchelU Ulrich 

 *Callopora muUitabulata Ulrich. 

 Rhynchotrema inequivalvis Castelnau. 

 Leper ditiafabulites Conrad. 

 Aparchites neglectus Ulrich. 



This list is evidence of the equivalence of the Nipissing strata with 

 the Black River strata of Minnesota and Iowa. The species marked 

 with an asterisk occur in the Baltic deposits, where also nearly every 

 one of the other bryozoan forms is represented by a variety or closely 

 related species. 



Middle Ordovician faunas are known from a number of localities 

 in the far North. These areas have been discussed and the fauna of 

 the most important fossiliferous locality, Silliman's Fossil Mount, at 

 the head of Frobisher Bay, Baffin Land, has been described by 

 Schuchert in an article entitled "On the Lower Silurian (Trenton) 

 Fauna of Baffin Land." ^ These various localities have been regis- 

 tered upon the accompanying paleogeographic map (fig. 3), and Schu- 

 chert's conclusions as to the extent of the deposits and his summary 

 of results are copied below: 



From the foregoing description of localities it appears that Middle Lower Silurian 

 horizons are very extensive in eastern Arctic America. Such are known in places 

 on either side of Hudson Strait, Frobisher Bay, the interior of Baffin Land, and to the 

 north of this land at various localities between latitudes 79° and 80° north. As far 

 as known, these strata unconformably overlie very ancient crystalline rocks, and are 

 in turn overlain by Upper Silurian beds of Niagara or Wenlock age. Lower Cambrian 

 rocks are found in southern Labrador, but in the region of Baffin Land such are not 

 known to be present. Here, then, there seems tol)e a complete break from the Lau- 

 rentian to the Trenton, followed by another break paleontologically, in the absence 

 of the Cincinnatian beds, and probably the lower horizons of the Upper Silurian. 

 The Lower Silurian fossils of this area indicate nothing older than the typical Tren- 

 ton of New York and the Galena of Wisconsin and Minnesota, and nothing younger 

 than the Utica stage of the United States. The thickness of these beds is not less than 

 900 feet, and probably exceeds this. 



This summary is based on information known to the author, and, while the evidence 

 is meager, the essential geological age and the sequeiice of the rocks of Baffin Land 

 seem to be established [pp. 148-149]. 



The only Lower Silurian horizons known in northeastern Arctic America are of 

 Trenton and Utica age. The latter zone appears only on the north shore of Frobisher 

 Bay, but the Trenton is found in various places from the north shore of Hudson Strait 

 to latitude 81° north. The Lower Silurian is thickest on Akpatok Island, where it is 

 from 400 to 500 feet in depth. Dr. Bell, however, estimates the entire thickness of 

 these strata in this region to be not less than 900 feet. 



1 Proc. U. S. Nat. Mus., vol. 22, 1900, pp. 143-177. 



