48 
ceous, of Radiolaria and Spongida. All of these marine de- 
posits which I have examined or heard of, were fossil in 
character, and all of those whose geological position has been 
determined with exactness, are considered as belonging to the 
Miocene Tertiary. 
But besides the marine deposits, we have others which 
occur much more commonly all over the world. These Iam 
now in the habit of calling ‘‘ Lacustrine Sedimentary” de- 
posits, in preference to ‘‘Sub-Peat,” a term I proposed for 
them some years since, and which has come into very general 
use. This term had been suggested by the finding of most 
such fresh-water deposits beneath peat, but of late years, 
several have been discovered at the bottoms of ponds and 
lakes where no peat exists, and the Diatomaceous stratum 
makes itself evident as an almost white cloud, when the bot- 
tom of the pond is stirred by means of a pole or the oar of a 
boat. But, as it appeared to be necessary that there should 
be a considerable extent of comparatively still water for the 
formation of such deposits, the term ‘“ Lacustrine Sedimen- 
tary” had been chosen as more appropriate. Such deposits 
are extremely common in this country, as well as in Europe, 
and are generally of a light grey color, or perfectly white, 
and extremely light and pulverulent in texture. On our 
Western coast, through California, Oregon, Washington 
Territory and Nevada, there exist vast tracts covered by 
fresh water deposits of Diatomacez, which are hard and 
stony. They have become so by the action of superimposed 
lava and basalt. Now it isa remarkable fact, that there have 
come to light two deposits from our Atlantic coast, possessing 
very. much the same physical characters as these Western 
strata; that is to say they are hard and stony, and almost 
white in color. One of these was presented at a meeting of 
the Lyceum some time since, by Dr. L. W. Feuchtwanger, but, 
unfortunately its exact locality has not been ascertained. 
The other is from New Hampshire, and all of the facts con- 
nected with its manner of occurrence, doubtless will be 
brought to light, as I am at present engaged on the micro- 
