io Bulletin 28 162 



Area idonea. Most of these species are peculiar to the St. Mary's, 

 but a few have continued up from the Choptank and the Calvert, 

 or are there represented by closely related forms. None of these 

 species are known, except in a modified form in higher beds 



General Correlation 



In Virginia and North Carolina, the Murfreesboro stage is 

 distinguished by having an Upper Miocene fauna associated with 

 a small percentage of species which have continued up from the 

 Lower Miocene, and a few which are peculiar, and therefore con- 

 stitute index fossils. By means of these index fossils, and the 

 general evidence furnished by the whole fauna, correlation with 

 more distant Miocene deposits becomes possible. 



For many years Tertiary beds have been known on Gay 

 Head, Martha's Vineyard, Massachusetts, and a part of this 

 group belongs to the Miocene series. Dall*, in 1894, visited the 

 locality for the purpose of studying the fauna. He listed about 

 thirty-three species of fossils of which twenty-two are mollusks. 

 Significant species, and correlating with more southern Miocene, 

 are Cardium virginianum, an index fossil of the Murfreesboro 

 stage, and Glycymeris reflexa of the Murfreesboro and Yorktown. 

 The beds therefore seem to be of Murfreesboro age, a conclusion 

 which Dall himself practically reached. His statement is as fol- 

 lows: "As regards correlation with the divisions of the Southern 

 Miocene it may be said 1 : that the Gay Head Miocene is Chesa- 

 peake and not older; and 2, that it belongs in all probability to 

 the upper part of the Chesapeake, certainly not lower than the 

 St. Mary's fauna, and probably between that and the Yorktown 

 beds." 



In Florida, Miocene deposits are exposed in a narrow belt 

 extending across the northern part of the state. During their 

 deposition, a strait existed which connected the Atlantic with the 

 Gulf and severed Florida from the mainland. 



* American Journal of Science, vol. 48, pp. 296-300. 



