TRANSACTIONS OF WAGNER 

 1562 



TERTIARY FAUNA OF FLORIDA 



States.* This being the type locahty, the name must be restricted to such 

 beds as are definitely homologous with those at this place, not merely in litho- 

 logical composition, but in age and relative position. For other formations, 

 however lithologically similar, the name should be rejected as being a source 

 of confusion, misunderstanding, and error. 



The true Grand Gulf beds in Mississippi, according to Miss Maury, con- 

 tain abundant remains of palms, deciduous and coniferous trees. A cast of a 

 Unio and other fresh-water bivalves and portions of the shell of a tortoise are 

 the other recorded fossils. In Louisiana, on the other side of the alluvial plain 

 of the Mississippi, these beds reappear and pass across the State in a south- 

 westerly and westerly direction into Texas. Very recently in Grand Gulf beds, 

 at Chalk Hills near Rosefield, Louisiana, Professor Harris found a number of 

 Unionidse in a layer only five or six inches in thickness. They are in the form 

 of casts very much distorted, so that their nature is barely recognizable. They 

 are associated with leaves of willow, birch, and other deciduous trees. Two 

 species of Unio and one of Anodonta have been described from this forma- 

 tion by Miss Maury. 



The present distribution of the successive Oligocene strata does not give 

 any satisfactory evidence of a marked embayment in the vicinity of the Chat- 

 tahoochee thalweg. Doubtless there was a small sinuation of the coast, but 

 nothing distinctive, as may be seen by consulting Miss Maury's map. The 

 brackish-water perezone seems a mere extension of that characteristic of the 

 Mississippi embayment. An immense drainage has been persistent here dur- 

 ing the greater part of Tertiary time, gradually extending its southern border 

 seaward from the continental shores. At its eastern extreme, which is mapped 

 about one hundred and fifty miles westward from the Chattahoochee, it merges 

 with the contemporaneous marine sediments. And this continues from the 

 base of the Chattahoochee Group to the upper Miocene or lower Pliocene, a 

 period perhaps of millions of years, during which there were two almost com- 

 plete replacements of the fauna, indicating profound geological changes in the 

 vicinity of the continent. During this period the two Americas were united, 

 the continental shore advanced to the Floridian archipelago, great ocean cur- 

 rents modified in their courses, and almost the whole congregation of warm- 

 blooded terrestrial vertebrates evolved. A geological view which would unite 

 under the name of one formation or group the sediments which were laid 

 down during a stretch of geological time including such extraordinary changes 



* Bull. Am. Pal., iii., p. 75. 1902. 



