Richmond Group of Cincinnati Anticline. — Focrste. 359 
The section of the genus represented by Strophomena nut- 
ans, Str. rugosa, Str. subtenta, Str. vetusta, and Sir. neglecta, 
may have entered the Cincinnati area from some other direction. 
No species representative of this section have so far been dis- 
covered in the Utica or Lorraine in the area under discussion. 
The greatest number of closely related species known is found 
in the Trenton and Cincinnati series towards the northwest, in 
Minnesota and neighboring states. 
The genus Dinorthis is unknown in the Cincinnati series of 
the Cincinnati region until the middle o'f the Warren bed is 
reached. Here Dinorthis retrorsa is found. At Madison in In- 
diana the vertical range is confined to a few inches of clay. 
Along the northeastern line of outcrop in Ohio it has a vertical 
range of several feet. Its nearest relative is a smaller form 
occurring in the Trenton at Ottawa in Canada. Dinorthis sco- 
villei and D. snbquadrata may represent migrations from the 
northwest. At any rate the most complete series of forms in- 
termediate between Dinorthis snbquadrata and the Trenton 
representatives of this genus so far known occur in Minnesota 
and neighboring states.* 
Between Hebertclla bcllarugosa in the Trenton and H. in- 
sculpta at the top of the Lower Richmond, there is a great 
interval, but both species are distinctly western. f The narrow 
vertical range of Hebertella insculpta in Ohio and Indiana sug- 
gests its introduction into the fauna of those regions through 
migration. Hebertclla occidentalism which occurs in the Mid- 
dle and Upper Richmond, is also a distinctly western species. 
Caty::yga headi, on the contrary, finds its nearest relatives 
towards the northeast. 
The massive corals, Cohunnaria alveolata, Cohunnaria halli, 
Calopoecia cribriformis, and Tetradiuni niinns are essentially 
Trenton forms which are absent in the lower and middle parts 
of the Cincinnati series, but are abundant at certain levels in 
the upper part of the Cincinnati group. This is also true of 
Protarea vetusta and Strcptelasnia rusticiun. Their migration 
during the later part of the Cincinnati epoch was probably 
from the north, but there is nothing to suggest whether from 
the northeast or the northwest. 
» Ibid., pp. 4,24,-431. 
t Ibid., pp. 434-435. 
