94 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 64 



Although there is need for additional study of the factors that accelerate, 

 retard, or inhibit the formation of spherulites and the growth of the grains, 

 the empirical facts in the process of the formation of the Floridian and 

 Bahaman oolites are demonstrated. They are as follows: (i) Denitrifying 

 bacteria are very active in the shoal waters of both regions and are precipitating 

 enormous quantities of calcium carbonate which is largely aragonite; (2) 

 this chemically precipitated calcium carbonate may form spherulites which by 

 accretion may become oolite grains of the usual size, or it may accumulate 

 around a variety of nuclei to build such grains 



Drew's unfortunately incompleted studies of the distribution of denitrifying 

 bacteria have shown them to be the most prevalent in the shoal-waters of the 

 tropics. They therefore conform to the principles enunciated by Murray for 

 the distribution of lime secreting organisms. By combining the results of 

 Drew and Murray, the deduction seems warranted that great limestone 

 formations, whether they be composed of organic or of chemically pre- 

 cipitated calcium carbonate, were laid down in waters of which at least 

 the surface temperatures were warm, if not actually tropical. 



Application. — The limestones of the Newland formation have 

 more or less magnesian content, but many of the layers are pure 

 limestone especially those containing the reefs or banks of algae. 

 The specimens of a\gx are usually magnesian and siliceous which 

 accounts for the weathering in relief, and the ease by which they 

 are brought into relief by the solution of the limestone in weak 

 hydrochloric acid. 



The purer limestones are of considerable vertical thickness and their 

 distribution indicates bodies of water several thousand square miles in 

 area. The banks or reefs of algal deposits make a small percentage 

 of the total mass of limestone, but if we assume, as I think we may, 

 that the Bacteria were active agents in the deposition of the soluble 

 bicarbonate of lime in the Algonkian waters, a plausible explanation 

 is found for the occurrence of the homogeneous limestones of the 

 Algonkian in which no traces of fossils have been found. The 

 presence of a well-developed Blue-green algal flora in the Algonkian 

 limestones prepares one for the view that the still more primitive 

 Bacteria were in existence and at work in the epicontinental Algon- 

 kian waters. 



Dr. Gement Reid in an article on Pal?eobotany states that :' 



the first evidence for the existence of Palaeozoic Bacteria was obtained in 1879 

 by Van Tieghem, who found that in silicified vegetable remains from the Coal 

 Measures of St. Etienne the cellulose membranes showed traces of subjection 

 to butyric fermentation such as is produced at the present day by Bacillus 

 Amylobacter ; he also claimed to have detected the organism itself. Since that 

 time a number of fossil Bacteria, mainly from Palaeozoic strata, have been 

 described by Renault, occurring in all kinds of fossilized vegetable and 



Ency. Brit., nth ed., Vol. 20, 1911, p. 525. 



