76 
Tne American Geologist. 
February, 1896 
sediment here represents in time of deposition 1,000 feet, or 
more, nearer shore; as for instance in New York the phos¬ 
phate of lime included in 1,000 feet of sediments might well 
make a layer one, two, or four feet thick if accumulated over 
the same area devoid of other sediment. And this could be 
true whether the deposits are of organic or inorganic origin. 
If organic, however, it would seem to accord best with the 
theory of accumulation from the settling down to the ocean 
bottom of the remains of free-swimming marine animals, such 
as fish. The same thing would happen if free-swimming 
shelled animals, such as the minute Foraminifera, were phos¬ 
phate of lime secreting. Perhaps the specimens of Cyclora 
found in these rocks resembled Foraminifera in this free- 
swimming feature. However this may he, it certainly seems 
a demonstrated fact that fossils of certain species of Cyclora 
are always richly phosphatic. On account of their association 
with phosphate of lime deposits in Tennessee and Kentucky, 
some of which deposits are Coming into importance as sources 
of commercial fertilizers, these species may he considered as 
valuable “ Leitfossilen ” for the identification of such deposits. 
State College of Kentucky , Dec., 1895. 
THE BUCHANAN GRAVELS; AN INTERGLACIAL 
DEPOSIT IN BUCHANAN COUNTY, IOWA. 
By Samuel Calvin, Iowa City, Iowa. 
(Plates IV and V.), 
About three miles east of Independence, Iowa, there are 
cross-bedded water-laid deposits of sand and gravel of more 
than usual interest. The beds in question occur near the line 
, of the Illinois Central railway. The railway company indeed 
has opened up the beds and developed a great gravel pit from 
which many thousands of carloads have been taken and used 
as ballast along the line. 
Overlying the gravel is a thin layer of Iowan drift, not more 
than two or three feet in thickness, but charged with gray 
o-ranite boulders of massive size. Some of these boulders may 
be seen perched on the very margin of the pit, and some have 
been undermined in taking out the gravel and have fallen to 
the bottom. The surface of the whole surrounding region is 
thickly strewn with Iowan boulders. It is evident that the 
