Cxlii CORRELATION OF MARYLAND MIOCEXE 



Atlantic coast of America subsequent to the Cretaceous. A cool-tem- 

 perate fauna for the time replaced the subtropical one normal to these 

 latitudes, and has left its traces on the margin of the continent from 

 Martha's Vineyard Island in Massachusetts south to Fort Worth inlet 

 in East Florida, and westward to the border of the then existing Missis- 

 sippi embayment. This seems to have been the limit of effectual invasion 

 by the northern marine fauna since, though no outcrops occur, the Gal- 

 veston artesian well-borings show two thousand feet of Miocene sedi- 

 ments west of the Mississippi, including a marked remnant of the Pacific 

 fauna, cut off from its allies by the elevation of Middle America and 

 barely surviving on this coast until the upper IMiocene time. The pre- 

 ceding Oligocene fauna has left traces as far north as southern Xew 

 Jersey, but denudation so accompanied the Miocene elevation that little 

 sediment of this epoch has survived in situ north of Georgia, and even 

 the Miocene sediments between northern Florida and Korth Carolina 

 are represented chiefly by isolated patches in sheltered areas. The deep 

 embayment of the Chesapeake region in Maryland and Virginia has 

 retained the largest and least disturbed area of the marine Miocene 

 sediments and given its name to them, as typical, on the Atlantic coast, 

 of the faunal remains of this character, which they contain. Contrary 

 to the conditions existing in Europe, in America no marked invasions 

 by the sea or extensive depressions of continental land are characteristic 

 of Miocene time, though in special localities the Miocene sediments 

 transgress the remnants of the Eocene. In the western region some 

 analogy may be found for the brackish water deposits of Europe, in the 

 Miocene lake beds and their vertebrate remains. Between the upper 

 Oligocene of the John Day beds of the West and the typical Chesapeake 

 (Loup Fork) Miocene, Scott has recognized in the Deep Eiver verte- 

 brates a fauna strictly analogous to that of Sansans (Gers) in France, 

 placed by Deperet, Gaudry and De Lappareut with the Helvetien. The 

 latter author recognizes in the Miocene of Europe the following stages : 



1. BuRDiGALiEN. — This group has been the occasion of more or less 

 controversy, and is introductory to the fully typical subsequent stages. 

 Whether it is really a consistent whole, is, and has been for some time, 

 a debateable matter. It is not improbable that some part of the beds 

 included in this stage by many European geologists correspond to part 



