Cyclora and Phosphate of Lime Deposits. — Miller. 75 
attention to the phospbatic layers in the vicinity of Lexing- 
ton.* The results were as follows: 
Cyclora casts. Rock. 
P 2 3 Ca 3 (P0 4)2 P,0 5 Ca :J (P0 4)2 
Tennessee (Devonian) specimens. .. .28.0 61.0 11.90 26.0 
Covington (Hudson River) specimen. 22. 7 49.5 .77 1.7 
Lexington (Trenton) specimen Very rich. 8-30 17.5-65.5 
It seems evident from the foregoing that the casts of Cyclora 
are invariably rich in phosphate of lime, having indeed, in 
most cases, very little carbonate in them. And one can hard- 
ly resist the conclusion that in some way the phosphate owed 
its extraction from the sea water to these minute marine 
gasteropods. That the hollow shells simply offered con- 
venient receptacles for the storing of these deposits hardly 
seems reasonable. It is true that phosphate of lime tends to 
collect in concretionary forms; the phosphatic nodules of 
South Carolina, those found scattered through the Black 
shale of Tennessee and Kentucky, and those underlying the 
Silurian Preston ore beds of Bath county, Kentucky, are all 
well known instances of this. Even where it exists in minute 
grains, as in the Tennessee phosphate, these appear to be con- 
cretionary in nature. But why should the molecular forces 
seize upon the hollows of certain species of gasteropod shells 
in which to display their concretionary tendencies? 
Professor SafFord's theory to explain the accumulation of 
phosphate deposits in pre-Carboniferous sediments is certainly 
ingenious and at the same time simple. It has much to com- 
mend it. The facts brought out by the deep sea explorations 
of the Challenger expedition are in accord with it. Briefly 
stated it is as follows : 
Phosphate of lime accumulation at the bottom of the sea i< 
in inverse ratio to the rate of sedimentation. In Tennessee 
and Kentucky we have Silurian and Devonian rocks which 
were deposited in an open sea remote from land. One foot of 
*Attention was first called to the phosphatic limestone layers in the 
Blue Grass beds of the Trenton limestone by the late Dr. Robert Peter, 
chemist of the Kentucky Geological Survey and father of the Dr. Peter 
mentioned above. The report of the analyses published in 1877 calls 
especial attentioD to the richness of these layers and the presence in 
them of "many microscopic marine univalve shells." lie also com 
mented upon the presence of phosphates in these upper Trenton beds 
and made them the main cause of tl great and durable fertility of 
the Blue Grass soil." 
