360 The American Geologist. •^"''''^' ^''"'^"^• 
Beatricea imdidosa and Bcatricca nodiilosa range from the 
Trenton nearly to the top of the Ordovician on the island of 
Anticosti, but in Kentucky they are found only near the top of 
the Lorraine and in the Richmond. 
The preceding observations suggest that an important part 
of the fauna of the Richmond stage, as represented in Ohio, 
Indiana, and Kentucky, was not developed from the Lorraine 
fauna of the same area but entered this field from some more 
northern territory as the result of migration. This part of the 
Richmond fauna has a distinctly Trenton facies. Since the 
greater number of varieties intermediate between the charac- 
teristic Trenton species and their Richmond representatives 
appear to be preserved in the Trenton of the northwestern 
states, Minnesota, Iowa, Illinois, Wisconsin, Manitoba, and in 
the Trenton of Ontario and eastern Canada, it seems probable 
that this part of the Richmond fauna was developed chiefly north 
of the present Ohio basin, and presumably within the terri- 
tories designated. From these territories that part of the Rich- 
mond fauna here under consideration appears^ to have entered 
the Ohio basin by at least two routes : one from the northwest 
bringing in the rugosa group of Strophoinena, Dinorthis siib- 
qiiadrata, and possibly Hehertella inscitlpta, and another from 
the northeast, bringing in Dinorthis retrorsa, and Beatricea. The 
migrations from the northeast appear to have begun in the lat- 
ter part of the Lorraine, and to have taken a path which was 
cut off from New York, so that the Richmond fauna did not 
enter that state or the Appalachian region.* The migrations 
from the northwest appear to have begun later but to have been 
more influential in determining the chief characteristics of the 
Richmond fauna. The derivation of the typical Richmond 
fauna from some more northern areas is not inconsistent with 
the existence of some of the Trenton ancestors within the Ohio 
basin during Trenton times, since the Trenton fauna may have 
retreated towards the north at the close of the Trenton, and 
given way to the Utica fauna which marks the l:)eginning of 
the Cincinnati epoch. 
Some of the forms of brachiopods occurring in the Cin- 
cinnati series of the Ohio basin are probably largely the result 
* Paleozoic seas and barriers. Ulrich and Schuchert. Report of New- 
York State Paleontologist for 1901, published in 1902, No. 2. 
