Mesozoic and CcBnozoic Geology and Palaeontology. 229 



meridian. In the same region, on hills 300 feet high, are roches 

 moutonnees with their smoothest faces pointing in the same direction, 

 or to the northwest. This direction is that of the valley or gorge of 

 the Saguena}'-, which enters nearly at right angles the valley of the 

 St. Lawrence. 



In like manner at Murray Baj^, there are striae on the Silurian lime- 

 stones near Point au Pique, which run about N. 45° "W., but these 

 are crossed by another set having a course S. 30° W., so that we 

 have two sets of markings, the one pointing upward along the deep 

 valley of Murra}^ Bay river to the Laurentide hills inland, the other 

 following the general trend of the St. Lawrence valley. The Bowlder 

 clay which rests on these striated surfaces, is a dark -colored till, full 

 of Laurentian bowlders, and holding Leda truncata, and also Br^'-ozoa 

 clinging to some of the bowlders. In ascending the Murray Bay river, 

 we find these bowlder beds surmounted by very thick, stratified clays, 

 with marine shells, which extend upward to an elevation of about 800 

 feet, when the}' give place to loose bowlders and unstratified drift. 



The Bowlder clay over a large portion of the plain of Lower Canada 

 is succeeded hy the Leda cla}-, which varies in thickness from a few 

 feet to 50 or perhaps 100 feet. The material of the Leda clay is of 

 the same nature as the finer portion of the paste of the Bowlder clay, 

 and the latter seems to graduate into the former. It sometimes holds, 

 hard, calcareous concretions, which, as at Green's creek, on the Ottawa, 

 are occasionally richly fossiliferous. When dried, the Leda clay be- 

 comes of stony hardness, and when burned, it assumes a brick red col- 

 or. When dried and levigated, it nearl}^ alwa3'^s affords some foramin- 

 ifera and shells of ostracoids; and in this, as well as in its color and 

 texture, it closely resembles the blue mud now in process of deposition 

 in the deeper pai-ts of the Gulf of St. Lawrence. It extends west to 

 where the Laurentian ridge of the Thousand Islands crosses the St. 

 Lawrence, and where the same rocks cross the Ottawa, and in gen- 

 eral may be said to be limited to the Lower Silurian plain, and not to 

 mount up the Laurentian and metamorphic hills bounding it. 



The Saxicava sand sometimes rests upon the Leda clay, sometimes 

 upon Bowlder clay, and often on the older rocks. In some instances 

 the surface of the Leda clay has been denuded and cut into deep 

 trenches, and the sand rests abruptl}' upon it; in other cases there is a 

 transition from one deposit to the other, the clay becoming sandy and 

 gradually passing upward into pure sand. It must have been origin- 

 ally a marginal and bank deposit, depending much for its distribution 



