Revieivs — C. Siruckmann — The Wealden of Hanover. 281 



fresh-water or terrestrial shells, are recorded in a few instances, 

 apparently always within the lower till, but generally near its upper 

 surface. The superposition of glacial drift upon decomposed gneiss 

 and granite is noted. 



Much attention has been given to the gigantic terminal moraine 

 stretching in a sinuous line across Minnesota, and Dakota, and 

 thence north-westward far upon the Saskatchewan plains in tlie 

 adjacent British territor3^ The same moraine has already been 

 traced across Wisconsin by Prof. T. C. Chamberlain, the director 

 of the Geological Survey of that State, and is belipved to exist also 

 in Illinois, Indiana, Ohio, Pennsylvania, New York, and New 

 Jersey. Beyond it has been explored by Upham along the north 

 shore of Long Island, through Khode Island, and along Cape Cod. 

 The moraine thus appears to stretch, though with several interrup- 

 tions, across more than half of the continent. It lies near the 

 southern limit of ice-action in the east; but in the west it is fully 

 three hundred miles north of that line. 



The silty deposits of the Eed River Valley are described in some 

 detail ; and the exploration of their origin is a valuable contribution 

 to the glacial theory. It is suggested that as the ice-sheet retreated 

 over surfaces sloping to the northward, the waters derived from 

 its dissolution accumulated in all depressions to the level of the 

 south-lying divide. Such an accumulation is supposed to have taken 

 place in the vast basin occupied by Eed Eiver and Lake Winnipeg ; 

 and for it the very appropriate name of LaTce Agassiz is proposed. 

 The silts of the region are regarded as the finer glacial debris 

 suspended in, and finally precipitated by, the waters of this lake. 

 The conception embodied in this hypothesis appears to have been 

 first grouped, though in a general way, by N. H. Winchell. It 

 seems to afford the first satisfactory \z.ey to a rational explanation 

 of the stratified deposits so generally found on northwardly sloping 

 glaciated regions. W. J. M. 



IV. — Die Wealden-Bilditngen der Umgegend von Hannover 



EiNE geognostisch-palaontologisch-statistische Darstellung 

 VON C. Struckmann. Mit fiinf Tafeln Abbildungen. Hahn'sche 

 Buchhandlung, 1880. 



THE author of this interesting work is already favourably known 

 to our readers by " Der Obere Jura," reviewed in our volume 

 for 1879. The Monograph now before us is a detailed description 

 of the Wealden formation from the beds resting upon the Portland 

 Limestone to the Hilsthon of the Chalk, near Hanover. The 

 Wealden is divided into three stages, each forming a well-marked 

 horizon of life. 



I. The deepest is the " Munder or bunte Wealden-Mergel," 

 representing the Purbeck beds of English geologists, and consisting 

 of thick beds of limestone interstratified with beds of marl, in 

 "which are numerous specimens of Exogyra virgida, fossils are rare, 

 the most abundant is Corhula mosensis, Buv. They attain a thickness 



