NEGATIVE CONTINENTAL ELEMENTS 457 



Only during Middle and Upper Ordovicic times was there connection with 

 the Saint Lawrence sea north of Adirondackia. Subsequent to the Ordo- 

 vicic the main topographic features of the Mississippian sea were the 

 islands of the Cincinnati uplift and the other islands or peninsulas Mis- 

 souria, Wisconsia, Kankakeia, and Alleghania. These were low lands 

 more or less subjected to marine inundations. Cincinnatia, Missouria, 

 and Wisconsia were the most persistent, and all of these lands had their 

 origin in movements previous to the Middle Mohawkian of the Ordovicic. 



Outside of the Oklahoma basin the deposits of the Mississippian sea are 

 far less in thickness than those of the northern Appalachian trough or 

 the Great Basin of the Cordilleran sea. In the main they consist of cal- 

 careous shales and limestone often inclosing a profusion of fossils. The 

 strata are often warped and rarely folded (exception, the Wabash axis), 

 but in places there is considerable faulting. 



The constantly changing topographic features of the Mississippian 

 sea cause its deposits and faunas to be much localized and variable. 

 These conditions make the work of the biologist all the more interesting, 

 because difficult. 61 To facilitate the description of these localized sedi- 

 ments and faunas it is necessary to name the various basins bounded by 

 the featureless lands. The Mexico mediterranean effected a wide entrance 

 through the Mexico embayment between Llano and Appalachia, an area 

 now deeply buried beneath post-Paleozoic deposits. Northeasterly this 

 embayment may have continued into the Indiana basin 62 to the west of the 

 Cincinnati uplift and east of Missouria and Kankakeia, or into the Appa- 

 lachian sea by way of the Cumberland basin. The latter may also have 

 extended into the Ohio basin of Ohio and western New York on the east- 

 ern side of the Cincinnati uplift and west of Alleghania (a restricted 

 usage of Ohioan province 63 ), or the Ohio basin may have been in com- 

 munication with the Indiana basin around the north end of Cincinnatia. 

 During the Ordovicic and Siluric the Ohio and Indiana basins again may 

 have had open communication with the Ontario and James basins and the 

 Hudson sea. In Devonic times this northern extension did not pass 

 beyond the James basin, and in late Devonic the northern boundary of the 

 Mississippian sea was restricted to the Ohio and Indiana basins. At dif- 

 ferent times the latter basins were connected by Kentucky strait, which 

 passed across the Cincinnati uplift in Kentucky. 



During the Devonic Traverse basin (Schuchert, 1903, 150) became 

 the thoroughfare for the passage of the Cordilleran faunas of the Iowa 



61 Also see Dana regarding this. Bull. Geological Society of America, vol. 1, 1890, pp. 

 43, 44. 



62 Schuchert : American Geologist, 1903, p. 148. 



63 Ulrich: Professional Paper, no. 24, of the TJ. S. Geological Survey, 1904, p. 91. 



XLII— Bull. Geol. Soc. Am., Vol. 20, 1908 



