448 C. SCHUCHERT PALEOGEOGRAPHY OF NORTH AMERICA 



interior or Mississippi basin, and (3) the Western interior or that of the 

 Eastern Eocky Mountain slope" (1890: 41). These broad divisions still 

 hold good and with slight modification are adopted by the writer, the 

 shorter names applied by later stratigraphers, chiefly by Walcott, 38 being 

 employed. The "eastern interior sea" will be restricted to Dana's original 

 definition — that is, to the great Appalachian syncline east of Alleghania 

 and Tennesseia and west of Appalachia; for this area, Appalachian 

 sea will be used instead of Dana's original name, "Appalachian region." 

 "The central interior or Mississippi basin" of Dana includes the Tarious 

 local basins on either side of the Cincinnati axis, bounded on the east by 

 Alleghania and on the west by Missouria, Llano, Siouxia, and Wiscon- 

 sia. To this sea Walcott has given the name u Mississippian sea," follow- 

 ing Dana's earlier determination. "The western interior sea" W^alcott 

 has called "Cordilleran sea" while "the eastern border basin or region" of 

 Dana (1874: 146) is here changed to Saint Lawrence sea. 



These bodies of water and others to be named in the following pages 

 are distinct faunal provinces whose successive biota are received from 

 those great perpetual realms of marine life — the Pacific, Atlantic, and 

 Arctic oceans. They are the "negative elements" of Willis, 39 yet as the 

 oceanic areas are the true . negative elements the writer has designated 

 these seas as negative continental elements. They have been defined by 

 Willis as follows : "By contrast with the positive elements of the continent 

 which are recognized by absence of sediments and preponderance of un- 

 conformities, the negative elements are distinguished by the sediments 

 which bury them." 



According to the derivation of their faunas, these various elements or 

 seas may be grouped as follows : 



Seas with Atlantic or Poseidon life. — Primarily (1) Saint Lawrence, 

 (2) Potomac embayment; secondarily (1) Appalachian, (2) Mississip- 

 pian, and (3) Hudson. By inference, Suwanee strait. 



Seas with Mexico-Caribbean life. — Primarily (1) Gulf of Mexico over- 

 lap, (2) Coloradoan, and (3) Mississippian: secondarily, Appalachian. 

 By inference, Sea of Tehuantepec. 



Seas with Pacific life. — Primarily (1) Cordilleran, (2) Sonoran, (3) 

 Logan, (4) Calif ornian, and (5) Yancouverian ; secondarily, Alaskan. 

 At times primarily, but as a rule with slight Pacific incursions, Missis- 

 sippian. 



Seas with Arctic life. — Primarily (1) Hudson, and (2) Alaskan; sec- 

 ondarily, (1) Cordilleran, (2) Coloradoan, and (3) Mississippian. 





38 Walcott : Proc. American Association for the Advancement of Science, vol. 42, 1894, 

 pp. 129-169. 



39 Willis : Bull. Geological Society of America, vol. IS. 1907, p. 398. 



