34 The American Geologist. jau. isoo. 
represents approximately the position of the two terranes, and 
consequently the relative levels of the fresh and of the salt 
water. For a long time American geologists recognized that 
the deposits of marine shells are more recent than the drift of 
the upper lakes, and many of them for this reason have desig- 
nated them under the name of the second drift. On the other 
hand it is evident that these deposits differ in man}'^ respects 
from the modern alluvium ; and as they belong to a period 
when the distribution of land and water was very different 
from that in our time, I propose to designate them in the 
future under a particular name; and considering that they 
are especially developed in the basin of the St. Lawrence, we 
have adopted the name of Laurentian or Laurentian terrane. 
I shall consider myself fortunate if this name, which has been 
approved by the greater number of geologists of this country, 
obtains the sanction of the Geological Society of France. In 
one of my preceding communications I added some remarks 
upon the parallelism of this terrane with the Quaternary 
deposits of Europe. 
"Since then I am advised that the deposits of Norway, in 
which one finds these shells are as much as 1,000 feet high, 
according to Keilhau ; also that those of Sweden, with their 
Azar, are the analogues of our American Laurentian. There 
remain doubts to my mind with regard to the till of Scotland, 
because of its unstratified structure, and because no one has 
described any fossils from this epoch. But having learned 
from the papers of Mr. Smith of Jordan Hill, that it contains 
shells of recent species," and that the same species are found 
in the deposits of clay under the till, I no longer doubt that 
this is the same horizon, the coarse till with its flints and 
striated pebbles embedded in the mud being according to all 
appearance the same deposits as those near Brooklyn near 
New York, that of a local form of the Laurentian. The depos- 
its of the north of Germany that are distinctl}' stratified and 
contain the shells, must for a very strong reason be entered in 
the category of the Laurentian deposits. It remains now to 
' "The shells of the till or Boulder clay are arctic species which for the 
most part are not living at present in the seas of Scotland ; they are 
in ceueral placed above the boulder clay in the beds of laminated clay 
The modern shells actually living in the neighboring seas one finds 
upon the terraces and in the banks of sand above the clay that con- 
tains the arctic species." 
