Stratigraphy of the Cambro-Stlurian Rocks op E. Manitoba. 69 



12 inches in diameter. These break out readily, forming circular discs 

 much resembling crude grindstones. The name for this prominent 

 point on the lake may possibly have been derived from the finding of 

 these ; ' grindstones " on the shore as well as from the fact of there being 

 there the material (sandstone) from which grindstones could be manu- 

 factured. 



cat head beds. 



Above the lower mottled limestone are seen several sections of a 

 fine grained evenly coloured yellow dolomitic limestone with numerous 

 concretions or dark coloured chert filling cavities, apparently left by the 

 decay of corals or soft bodied animals. Examples of these beds are 

 seen in the high cliff at Cat Head and along the shore to Lynx Bay. 

 At the western end of the section three miles west of Cat Head the 

 cherty concretions attain large dimensions. Several aie over a foot in 

 length and one measured 2 feet by 10 inches. The lower beds are fine 

 grained, resembling lithographic stone and are very rich in fossil 

 remains. 



The total thickness of these beds, as observed on the lake, is 68 

 feet. This includes the top beds of Cat Head and Outer Sturgeon 

 Island which are similar in colour but coarser in texture, becoming finely 



crystalline. 



The area outlined on the sketch match is proposed as a diagram 

 of the theoretical outcrop of these rocks, but owing to the mantle of drift 

 exposures arenotalwaysto be had, thusinthesouthern part eastofSelkirkno 

 exposures of this series at the surface so far are known, but the existence 

 of similar beds is shown below the Selkirk rock in the drilling made for 

 a well at Selkirk. Similarly no exposures west of Big Island are known, 

 but on the beach on the westward side south of Icelandic River numer- 

 ous fragments of the fine grained rocks are found. On Fisher Bay 

 loose fragments are found on the islands, but the shores are all low arid 

 there are no rock exposures. The south point of Reindeer Island is 

 probably underlain by these rocks and fine grained yellow beds exposed 

 at the base of cliffs on the mainland southwest of this island may prob- 

 ably also belong to this series. The eastern end of Long Point is 

 covered with drift deposit, but near the northern end of the lake at the 



