148 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.xxii. 



be iipcessary to elimiuate such ideutificatious as liorizon markers from 

 the Upper Silurian local faunte. 



Thirdly, Receptaculites arcticus,^ R. occidentalism, and R. oweni are good 

 Lower Silurian horizon markers and are easily identified. Therefore 

 the writer accepts the presence of tliese forms as indicative of Lower 

 Silurian rocks. Such localities are Cape Louis Napoleon, Cape Frazer, 

 and the west coast of King Williams Island. 



From this evidence, it appears that to the north of Baffin Land other 

 areas of Trenton strata occur, and likewise that at Cape Louis Napoleon, 

 Cape Frazer, and on the west coast of King Williams Island, they 

 underlie the Upper Silurian beds. Probably, it is this occurrence 

 rather than the transportation by ice, which has led to the mixing of 

 the faunas. 



AJcpatolc Island. — The Trenton of Frobisher Bay and Lake Kennedy 

 apparently continues southward to Hudson Strait, where, in the vicinity 

 of Big Island, Receptaculites oweni was found by Dr. Bell on pan ice, as 

 described above. Another Trenton limestone area occurs more to the 

 east, and near the south shore of Hudson Strait, on Akpatok Island, in 

 Ungava Bay. Here Dr. BelP obtained 90 fossils of Trenton age. He 

 writes : 



The portion of the island wliicli I saw [northern end to middle of east side] con- 

 sists of unaltered gray limestone in horizontal beds, and it presents a perpendicular 

 ■wall 400 to 500 feet high all along. This sea wall is clear cut and the beds appear 

 thick and solid, but wherever their edges have been long exposed to the weather or 

 in the hillsides and ravines of the interior, they split up into thinner layers. Some 

 fragments observed in one place had the appearance of lithographic stone. * * * 

 This formation must here have a thickness of 900 feet above sea level, and there is 

 possibly a great additional thickness of Cambrp-Silurian rocks beneath the sea level. 



EXTENT OF THE ARCTIC TRENTON. 



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 vari- 

 ous localities between latitudes 79° and 80° north. As far as known, 

 these strata uncouformably 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 to be a complete break from the Laurentian to the Tren- 

 ton, followed by another break paleontogically, iu the absence of the 

 Cinciiinatian beds, and probably the lower horizons of the Upper 

 Silurian. The Lower Silurian fossils of this area indicate nothing older 

 than the typical Trenton of New York and the Galena of Wisconsin and 



1 The types of this species are in the British Museum, and Dr. Hinde in his work 

 on the ReceptaculitidfB (Quart. Jour. Geol. Soc, London, November, 1884, p. 845) 

 gives the horizon as Lower Silurian. 



2 Summary Kept, of Geol. Surv. Dept. for the year 1897-98, pp. 82, 83. 



