No. 6.] J. W. DAWSON — SILURIAN FOSSILS. 339 



older rock which have afforded no fossils, and which probably 

 underlie those just referred to and may be Lower Silurian beds 

 tending downward to the Cobequid series and connected with it. 



Rocks of this character are well developed in the basin of 

 Lake Murdoch, where, according to Mr. Gilpin, they are cut off 

 from the Blanchard ore-series by a fault on the southern side. 

 They are traceable to the eastward, apparently underlying the 

 beds associated with the " Webster" ore-bed, and are well seen 

 still further to the eastward on the upper waters of the French 

 River. These beds differ considerably in mineral character from 

 any others in the district, though resembling in this respect rocks 

 seen at the Blue Mountain, near Eden Lake, and on the East 

 Branch of the St. Mary's River. They contain thick beds of 

 Nacreous or Hydro-mica slates, coarse slates, sometimes having 

 a conglomerated or brecciated appearance, green chloritic or 

 epidotic rocks, quartzite and agglomerate, and felsitic rocks. 

 They have afforded no fossils, and appear to me to be quite dis- 

 tinct from the Upper Silurian formation. In the meantime they 

 may be connected with the Cobequid series, with the typical 

 rocks of which series they are certainly closely associated farther 

 to the eastward. 



One of the marked features of the Upper Silurian in the dis- 

 trict in question is the great development of bedded red hematite, 

 and of rocks more or less impregnated with this ore. With re- 

 ference to its origin, this ore is evidently a marine deposit, and 

 formed under conditions sufficiently favorable to marine life to 

 enable it to contain many shells of Brachiopods and remains of 

 other animals. It is probably a chemical deposit or precipitate, 

 and often assumes an oolitic structure. In the coarser or more 

 impure beds the little concretions of oxide of iron often surround 

 grains of sand, and the ore passes into a ferruginous sandstone. 

 The following section (p. 340), from a MS. Report of Dr. G. M. 

 Dawson, shows the great development of the lower bed in one of 

 its exposures. These deposits of iron ore apparently began locally 

 in an early part of the Upper Silurian period, and were continued 

 into the Lower Helderberg period, while in the western part of 

 Nova Scotia, in the Nictaux district, we have evidence of their 

 continuance into the Oriskany age. 



Another marked feature of these deposits is the absence of any 

 representative of the great Niagara limestone, and the consequent 

 passage upward of Clinton deposits into those of Lower Helder- 



