110 HONEYMAN GEOLOGY OF ANTIGONISH COUNTY. 



tion as In the extreme south of the county, while Arisaig is on its 

 northern boundary, we have a group of strata of Arisaig age. My at- 

 tention was first directed to this locality by finding a beautiful cast of a 

 Petraia Forresleri — Salter. Subsequent examination of the rocks on 

 the west side of the lake disclosed a set of strata with organisms of 

 a peculiar kind and different from any of our former acquaintance. 

 I found the Petraia in abundance and evidently characteristic, asso- 

 ciated with casts of strange orthes and rhynconella, and a trumpet 

 shaped cornulite. The containing strata rest on the syenitic rocks 

 of the spur of the Ohio mountain already referred to. Similar 

 Petraia, led to the discovery and identification of the same formation 

 at Arisaig, Marshy Hope, James river, and at Barney's river, French 

 river and East river in the county of Pictou, all occupying the 

 same position in relation to the syenitic, except at Arisaig, where 

 the strata in question are synclinal. These strata, which I designated 

 in the Arisaig group, a, are at Lochaber associated with other strata, 

 which appear lithologically identical, but are distinguishable into 

 Arisaig a, c, d, by the fossils which we find in the loose rocks. 

 In these we find the Homalonatus of c, the Dalmania Logani, Crania. 

 Acadiensis of D, and in situ at the side of the lake I have found 

 Nova Scotia Choiietcs of d. Succeeding the strata containing the 

 Chonetes and occupying the same relative position as the strata which 

 I consider as Devonian at Arisaig, is a very broad band of reddish 

 brown and grey argillaceous slates, which form an island in the lake 

 extending to Poison's lake and beyond it. In their strike they 

 extend to the west of Lochaber lake in the one direction, and 

 through South River lake and the river itself in the other direction ; 

 and at right angles to the strike they pass into Guysboro'. On the 

 western side of Lochaber lake there are magnificent exposures of 

 the brownish red strata, in the course of a small brook that enters 

 the lake. To the south of the brook there is a thick band of lami- 

 nated limestone, altered and contorted, containing blue fluor spar. 

 Between Lochaber lake and Poison's lake these slates contain veins 

 of quartz of considerable thickness, interspersed with plates of specular 

 iron ore, and at one of the streams that flow into South river grey 

 and brownish red slate is associated with quartzite, which con- 

 tain crystals of colourless quartz of considerable size and beauty. 

 We also find garnets at Poison's lake and rhombic duodecahedral 



