The Geology of Cincinnati. 65 
There is considerable variation in the different groups in 
the proportions of limestone and shale. Shale greatly pre- 
dominates in the Utica, but from the lower beds of the 
Lorraine on, the proportion of limestone gradually increases. 
This shows that there was a gradual change from more or 
less turbulent conditions prevailing at the close of the 
Trenton to the time of the Lower Richmond, when quiet seas 
permitted the accumulation of the materials for closely suc- 
ceeding beds of limestone. As the period came to a close, 
there came anew turbulent conditions. ‘The fauna of the 
different groups indicates the same succession of changes. 
The character and conditions of the sedimentation would 
naturally produce strata in which fossils are very abundant. 
As in the Trenton period preceding, the bryozoa are the 
most abundant form of life. The quiet interior sea in which 
these strata were deposited proved a most congenial home 
for this form of life. Some strata are literally made up of 
their remains. Next in abundance are the brachiopods. 
The fragments of the broken shells of the latter sometimes 
compose beds of considerable thickness. Less than four per 
cent of all the forms known from the Cincinnati period, and 
these forms are of course widely distributed and generally 
subject to considerable variation, are found to range through- 
out. The great bulk of forms have usually a limited vertical 
range. 
The following is a list of the forms which, as far as present 
knowledge goes, are found in all the groups of the Cincinnati 
period: 
CORLENTERATA. 
Labechia? papillata (James). (c) 
ECHINODERMATA. 
Iocrinus subcrassus Meek and Worthen, and varieties. 
BRYOZOA. 
Ceramoporella ohioensis (Nichol- Stomatopora arachnoidea (Hall). 
son). (c) (c) 
Stomatopora delicatula (James ). 
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