AMERICAN “GIEA CLATE. DEPOSITS: 275 
for this correlation are not very strong, and investigation may 
show them to be erroneous. It is not likely, however, that the 
beds upon the Don can be referred to any earlier period. They 
may be later. Should the beetle-bearing beds at the base of 
Scarborough Heights prove to be distinct from the molluscan 
beds on the Don, the former may perhaps be found equivalent 
to the Aftonian beds previously described. Whether the beds 
on the Don belong to the horizon suggested or not, it is certain 
that vegetal beds were formed in the interval of the retreat 
between the formation of the Iowa till and the formation of the 
Wisconsin till, and some of these less well developed and less 
known deposits must be looked to as a type of this interglacial 
horizon, if the Toronto beds prove unavailable. 
If the fossiliferous clays and shales on the Don belong to the 
interval between the Iowan and Wisconsin formations, they may 
be tentatively correlated with the Neudeckian of Geikie. 
The Wisconsin formation (= Mecklenburgian ?).—Overlying the 
interglacial beds above the Iowan deposit, comes the most 
massive of the American till sheets, occupying the larger part of 
the territory of the northern states and very large sections of 
Canada. This is distinguished by a series of gigantic terminal 
moraines, stretching across the country in an undulatory fashion 
already well known to students of the subject. There are at least 
two divisions of the moraine-bordered tills, with a somewhat 
notable interval between the two, during which there was con- 
siderable rearrangement of the frontage of the ice. Asa result 
of this, some of the later moraines run at large angles across the 
earlier ones, riding over them in a quite disregardful fashion. 
In like manner there occurs upon the northern plains of 
Germany a series of similar gigantic moraines associated with 
thick till sheets. There are also pronounced but less massive 
moraines in southern Scandinavia and Finland. The two series 
are interpreted as representing a single stage by Dr. Geikie, but 
to one at a distance, and without personal familiarity with 
deposits, the suggestion that they represent two episodes having 
some such relation to each other as the two subdivisions of the 
