550 C. SCHL" CHERT PALEOGEOGRAPHY OP NORTH AMERICA 



geologic age. About -400 species are known in the American "Lower 

 Carboniferous" and abont 200 in Europe, most of which occur in the 

 Mississippic. 



Appalachian basin. — In the northern Appalachian basin the Chemung 

 sea continued apparently without break into the Bradfordian, and for a 

 time maintained connection with the Atlantic by way of the Xew Jersey 

 straits. After the Bradfordian this opening was permanently destroyed. 

 It is probable that the brachiopods Clionopectus and Parapliorliynclius 

 are of Xorth Atlantic origin, for they occur in the Bradfordian at "War- 

 ren, Pennsylvania; later they migrated to Iowa, and there became domi- 

 nant in the earlier portion of the Upper Kinderhookian. In late Kin- 

 derhookian time, therefore, the Mississippian sea had these earlier and 

 independent faunas variously commingled. 



The TTaverly series of the northern Appalachian basin is a continuous 

 one from the Chemung to the close of the Mississippic. Above the Brad- 

 fordian it begins in clastic materials composed of shales, sandstones, and 

 some conglomerates. The faunas are as yet imperfectly known. As 

 Girty has given much time to the collection and study of these forms, his 

 correlations are here followed, and are given in the table of formations in 

 the column "East of Cincinnati axis" (1905, 5-7). The Marshall series 

 in Michigan is also representative of this basin and directly associated 

 with the TTaverly series, but no attempt has been made to correlate the 

 various beds. It is probable that a part of the Catskill series is likewise 

 of Bradfordian time. In the main these are continental deposits, but 

 they may have zones of estuarine sediments. The Pocono is also Missis- 

 sippic in time, and its deposits, which are chiefly continental with coal 

 beds, may begin as early as the Bradfordian. 



Cordilleran sea. — The Pacific and Arctic faunas are widespread in the 

 Cordilleran sea. The one best known is the Spirifer centronatus fauna of 

 the Pacific realm in the Madison limestone, which extends to Missouri in 

 the Choteau of Kinderhookian time. In the Yellowstone Park region 

 it persists with little change in the western Cordilleran sea through 1.600 

 feet of limestones. According to Girty. the Madison occupies the entire 

 time of the Mississippic period as here defined — that is, to the close of 

 the Keokuk. TTeller (1909, 282) states that "this fauna shows many 

 affinities with the southern Kinderhook faunas of the Mississippi val- 

 ley*' — that is, the Choteau. Girty (1899) reports that 37 per cent of the 

 Madison fauna is common to the two regions. It seems, however, that 

 this intercommunication ceased at the close of the Kinderhookian, as 

 nothing is known of the wonderful Burlington crinoid fauna in the west- 

 ern sea. The life of Lake valley, Xew Mexico, is now held to be older,. 



