106 THE CANADIAN NATURALIST. [Vol. Vlii. 



depth traversed by a powerful ocean current. It would 

 appear, therefore, that when these beds were deposited the 

 Acadian region was submerged, and that a resistless current from 

 the icy regions of the Pole flowed over it, sweeping the finer 

 parts of the Boulder-clay from the exposed hills and ridges to 

 more profound depths in the ocean, and heaping up the coarser 

 materials into "horsebacks" (escars) "moraine ridges" and 

 mounds, depending for their direction and form upon the position 

 of submerged elevations along the sea-bottom. Similar condi- 

 tions now prevail in certain parts of the North Atlantic Ocean, 

 where there are wide tracts of the ocean floor covered with sand, 

 having scattered stones and boulders, and which in like manner 

 are swept by strong currents flowing from the Polar regions. 



I would suggest for these Acadian beds the name Syrtensian r 

 as indicating their composition and the conditions under which 

 they were formed. Dr. Packard has used the same term in a 

 different sense ; viz : as a name for the fauna of a sub-arctic- 

 type which characterizes the fishing banks off the coast of New 

 England. 



Beds of the kind I have described above would appear to- 

 underlie the Leda clay in the broad plain of the St. Lawrence ; 

 for in Dr. Dawson's section of the modified drift at the Glen 

 brick-works near Montreal, he gives a thickness of twenty feet 

 of such beds beneath the Leda clay at that place. A similar 

 sub-stratum to the Leda clay is to be found along the Atlantic 

 coast of the United States as far south as Massachusetts Bay, 

 as appears from the figured sections and text of Dr. Packard's 

 memoir ; and it is clear from the writings of Prof. C. H. 

 Hitchcock and others, that this part of the Post-Pliocene is 

 similarly constituted as far south as Long Island Sound. 



The Syr ten si an beds of Acadia graduate upward into Leda 

 clay when the latter is present. This group consists of finely 

 laminated clay beds with thin partings of sand, near the coast ; 

 but among the hills of the interior it is chiefly made up of sand 

 and clay in alternate layers, and in nearly equal propor- 

 tions. In certain limited tracts away from the coast the group 

 contains only sand beds. Among the hills of the interior, organic 

 remains are but seldom met with in the Leda clay, but on the 

 lower levels near the coast a variety of fossils have been exposed 

 by the wearing of the clay banks along the shores of the Bay of 

 Fundy, and in cuttings along lines of railway. Among these 



