324 MINERALS AND GEOLOGY 



phates, etc., are not uncommon in some of their beds. The gypsum 

 is mostly of an earthy or granular texture, and is always more or 

 less mixed with carbonates. The formation enters Canada a short 

 distance above the Falls on the Niagara River, and includes the 

 whole of Grand Island in this portion of its area. From thence, 

 it follows the general outcrop of the Guelph formation to the vicinity 

 of the Saugeen "River on Lake Huron. It thus includes portions of 

 Welland, Haldimand, Brant, Oxford (north-east corner), Waterloo, 

 Perth and Bruce ; but throughout much of this area it is covered by 

 Glacial and other superficial deposits. Exposures may be seen near 

 Waterloo village, Bertie township, on the Niagara River ; along the 

 Grand River between Cayuga and Paris, and near the Don Mills ; 

 on the Upper Saugeen, near Ay ton and Neustadt, in Normanby 

 township ; around Walkerton on the Saugeen, in Brant, and at 

 various points down the river : as at the elbow in the south-west 

 corner of Elderslie, a little below Paisley. The gypsum or "plaster" 

 deposits are chiefly quarried at Cayuga, Indiana, and York, in the 

 township of Seneca; at Mount Healy and elsewhere in Oneida 

 largely around Paris ; and at various places in Brantford township. 

 Some of the dolomitic and argillaceous shales of the formation, as 

 those which outcrop near Walkerton, etc., furnish valuable material 

 for the manufacture of hydraulic cement ; and it is apparently from 

 this formation that the brine obtained in the vicinities of Goderich, 

 Seaforth and Clinton, by deep borings through overlying deposits 

 is essentially derived. 



The Lower Helderberg or Eurypterus Formation, as occurring in 

 this district, represents merely a small portion of the " Lower 

 Helderberg group " of New York. It is made up of a few thin- 

 bedded dolomites, with some interstratified shales and a brecciated 

 bed (composed chiefly of dolomite fragments) at its base. These 

 strata, which collectively do not exceed fifty feet in thickness, appear 

 to represent the lower portion the "Water-lime" or " Tentaculite 

 limestone" of the Helderberg series proper. They are chiefly 

 characterized by the presence of fragmentary examples of a peculiar 

 crustacean, Eurypterus remipes (fig. 180), belonging to the Mero- 

 stomata, an almost extinct order, but represented in existing nature 

 by the Limulus or Xiphosure. The formation probably extends as 

 a thin band along the western border of the Onondaga formation 



