GEOLOGY. 21 



two or three species. Near Bainbridge it is found forming the 

 bed of the river, and consists mainly of an aggregation of small 

 orbitulites of from one-eighth to one-third of an inch diameter, 

 with the occasional occurrence of species of the genera pecten, 

 crystillaria and cidaris. 



The White limestone forms the lowest portion of the Eocene 

 formation in Georgia. It varies much in consistency, passing 

 from a friable marl to a compact rock. The echinoderms and 

 corals abound in it : and it is in this formation that the remains 

 of the Zeuglodon have been found in Twiggs, Crawford, Wash- 

 ington and Decatur counties. As it produces a very good 

 lime, it is burnt, wherever it occurs, for that purpose. 



The Cretaceous formation is, with the exception of a small 

 patch at Saundersville, confined to parts of the counties of 

 Randolph, Stewart, Muscogee, Marion and Macon. Although 

 its existence in these counties is well established by character- 

 istic fossils, but little is known of the nature of the rocks in 

 which they are found. A. deposit in the Chattahooche in 

 Stewart county, from which the writer of this article, through 

 the liberal exertions of H. T. Hall, Esq. of Columbus, and I. 

 C. Plant, Esq. of Macon, obtained teeth of the Geosaurus, 

 Mosasaurus * of an extinct crocodile, Lamna plicata, Lamna 

 accuminata, and Galleus pristodatus, is identified with the fer- 

 ruginous sand formation of New Jersey, as well by the consti- 

 tution of the soil as by its fossil remains. 



On the Petalau creek in Randolph county, and at several 

 other points, Ammonites placenta, Exogyra costata, Belennites 

 Americanus, and a large Cucullia have been found. 



The Transition, or older fossiliferous rock formation has 

 been less explored than any other part of the geology of 

 Georgia : and in the present state of our knowledge the limits 

 of the groups composing it, cannot be designated with accu- 

 racy. It occupies the whole of the counties of Chattooga, 

 Walker, Murray and Floyd, the greater part of Cass, the 

 northern half of Paulding, and all of Dade, except some small 

 patches of coal in the Lookout and Raccoon mountains. That 



* A new species, described by Prof. R. W. Gibbes, as the Mosasaiirus Cou- 

 peri. 



