238 THE AMERICAN MONTHLY [July 



and spicules of sponges, richly intermixed and by the 

 manipulatory process recounted herein, the diatomace- 

 ous forms were removed in sufficient quantities for study 

 purposes. The phenomena of metamorphisation are well 

 shown in this deposit, as in the trituration process among 

 the larger coscinodiscus forms that come througli, a few 

 interlacing natural crystal plates embrace and hokl to- 

 gether across the central portion of the disc, leaving in- 

 terspaces between the plates. While many of the discs 

 have the metallic or coppery aspect of mineral pyrite; 

 others have embedded in their texture minute spherules of 

 pyrite, wliich appear as black spots by transmitted light 

 but golden by condensed surface light. The foraminiferal 

 shells have also undergone the change from carbonate of 

 lime to a mineral no longer soluble in acids, and tend- 

 ing more to a silicified product. In cases the crystalliza- 

 tion has obliterated the reticular marking of the discs, 

 while others have preserved the hexagonal areolation 

 enabling the species to be readily recognized. 



At St. Stephens, Ala., on the Tombigbee River, I 

 secured large blocks of the coraline white friable lime- 

 stone already celebrated in geology as a locality where 

 the chalky strata are made up of the large and conspicu- 

 ous foraminifera. Orbitoides mantellii imbedded in a 

 matrix of microscopic corals, the foramninifera in this 

 deposit yielding silicious casts or molds of the internal 

 chambers of the shells, after dissolving away the shell of 

 lime carbonate. In a more northerly direction, a further 

 extension of this chimney rock exists around the town of 

 Suggsville, also in Clarke Co., where I was enabled to 

 observe quantities of fossilized nodules known as copro- 

 lites, which weather out of the soft rock, and when 

 found in economic quantites are valuable on account of 

 their phosphatic nature. From these nodules thin trans- 

 parent sections may be made, showing the coprolites to 

 be an aggregation of forminiferal bodies ranging down 



