44 Bulletin 15 354 



Florida. Dr. Foerste surmises that this strait was at first compar- 

 tively shallow, but was scoured out by the erosive adlion of the 

 current. 



Depositions in the Chattahoochee and Mississippi embayments . 

 Meanwhile, the Chattahoochee river brought down sediments 

 which were mingled with shells along the shores and with material 

 brought by the ocean current, and its embayment* was the prin- 

 cipal scene of deposition of the Chattahoochee limestones and clays. 



In a similar manner, the Grand Gulf deposits were made in 

 the Mississippi embayment. The latter depositions, then, as now, 

 were singularly lacking in organic remains. 



Tropical fauna of Chipola7i waters. The warm current bath- 

 ing the shores made the Chipola period most favorable for mol- 

 luscan life. Species introduced by this current from the Antillean 

 watersf established thriving colonies. 



Intrtision of cold current. hitroduHion of Chesapeake species. 

 The continued elevation, however, gradually resulted in the 

 defledlion eastward and off-shore of the warm current, allowing 

 the passage alongshore of a cold current from the northeast. Dr. 

 FoersteJ supposes the cold current to have branched at the south- 

 eastern extremity of the continent; one portion flowing past the 

 Florida islands, and the other bathing the continental shores. 

 This change was followed by the disappearance of the Chipola 

 fauna, and the cold water fauna of the Chesapeake Miocene was 

 introduced. 



Dr. Dall notes] | the reappearance of the tropical Chipola 

 forms under the more favorable -conditions of the Pliocene of the 

 Caloosahatchie. 



* Johnson, the Chattahoochee Embayment, Bull. Geol. Soc. Amer., 

 vol. 3, 1892, pp. 128-132. 



fDall, Bull. U. S. Geol. Survey, No. 84, 1892, p. 30. 

 XAnier. Jour. Sci., 3rd ser., vol. 46, 1893, p. 246. 

 II Dall, Bull. U. S. Geol. Survey, No. 84, 1892, p. 30. 



