PHYSICAL AND FAUNAL EVOLUTION 243 
Euomphalopteris, Hormotoma, and Coelidium, together with various 
species of Eotomaria and other Pleurotomarioids, and the remarkable 
Trematonotus alpheus. ‘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. Tvimerella grandis, Megalomus canadensis, 
Pycnomphalus solariodes, Coelidium macros pira, and S phaeradoceras 
des plainense 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 
t See Savage, T. E.; Amer. Jour. Sci., Vol. XXV (1908), pp- 431-44; Schuchert, 
Jour. Geol.,; Vol. XIV (1906), pp. 728, 729. 
