78 AMADEUS W. GRABAU 



Euomphalopterus, Hormotoma, and Coelidium, together with various 

 species of Eotomaria and other Pleurotomarioids, and the remarkable 

 Trematonotus alpheiis. This represents a new invasion of the interior 

 sea, probably from the rich fauna of northern Europe. In North 

 America the physical conditions accompanying this spread of the 

 fauna appear to have been shoaling of the water and inclosure and 

 restriction of the interior sea. The fauna appears as early as the 

 lower Coral Bed in Wisconsin, while the Guelph element of the Racine 

 fauna is very marked. Trimerella grandis, Megalomus canadensis, 

 Pycnomphalus solarioides, Coelidium macrospira, and Sphaeradoceras 

 desplainense are among the species which occur in association with 

 the rich Racine fauna. Many of the typical corals, brachiopods, 

 and other types continue into the Guelph in Wisconsin, the fauna 

 not differing markedly from the Racine. In New York Clarke and 

 Ruedemann have found the Guelph fauna intercalated between the 

 normal manifestations of the Niagaran coral fauna (Lockport), 

 and it appears that in the Canadian type region alone does it occur 

 in its purity. 



THE ATLANTIC AND SOUTHERN NIAGARAN 



The Atlantic Niagaran has generally been recognized as belong- 

 ing to a distinct province separated by a land barrier from the interior 

 sea. This is made evident not only by the distinctness of the faunas, 

 as exhibited in the Anticosti group and the development in Maine 

 and New Brunswick, but also by the fact that the entire interior 

 Appalachian region contains only shallow-water or continental 

 deposits, indicating a continuous land mass in the East. That the 

 Anticosti fauna nevertheless communicated with the interior is shown 

 by its occurrence in Georgia and elsewhere in southeastern United 

 States. This occurrence represents either a distinct embayment from 

 the Atlantic, or the fauna migrated into the interior, going around the 

 southern end of Appalachia, which may then have been separated 

 from South America. An invasion of the interior from the south is 

 indicated by the fauna of the Cape Girardeau or Alexandrian^ forma- 

 tion of Illinois and Missouri, and perhaps also by the fauna of the 



I See T. E. Savage, Amer. Jour. Sci., Vol. XXV (190S), pp. 431-44; Schuchert, 

 Jour. Geol., Vol. XIV (1906), pp. 728, 729. 



