Ulrich on Correlation of the Lower Silurian. 107 
The Ostracoda and some of the Bryozoa are exceedingly 
abundant. Where these beds come to the surface red cedar is 
the prevaiHng tree. 
Beds IV. Resting upon the rocks just described, I find from 
twenty to twenty-five feet of decidedly cherty layers, the blocks 
of hornstone giving them a rugged aspect when worn. The 
soil formed by them is of a light red color. I have met with 
these layers onl}' in Mercer county, about two miles south of 
High Bridge, where they are shown in several small cuts along 
the Cincinnati Southern R. R. Here they consist of unequal 
but never thick layers, made more or less irregular by the horn- 
stone, which of itself may form irregular layers. Near the 
middle of the beds there is a very soft clay layer, about two 
feet in thickness, nearly white, with often a greenish tinge. 
Some fragments were seen in which the green color is decided. 
It has a peculiar unctuous feel, is readily cut with a knife, and 
when exposed a short time to the atmosphere breaks up into 
small flakes. 
Fossils are moderately abundant in these beds, but, so far as 
observed, occur only in or on the surface of the blocks of horn- 
stone. All are silicified, and the most of them very difficult to 
obtain in good condition. A species of Helicotoma^ ^\ hich 
seems identical with Pleurotomaria rniiucria Billings, is very 
common. The other fossils are: 
JieUcotoma u. s/>. (a) (also in di\ i-ion Orthis bellarugasa Conrad. 
3-) Coliimnaria halli Nich. 
Murc/iisonia frirartiKita \ia\\. (^=C. alveolata, American authors. 
OrtJioceras (4 or 5 undet. spe ies.) non Goldfuss. 
Cyrtoceras planodorsafinn \V'^hitfield. Stromatocerium ri/gosiiin Hall. 
CaniercUa pandcri Bill. Calatliium formosuin Bill. 
Beds V. Succeeding beds IV we find a series of heavy bed- 
ded, coarse, sub-crystalline, gray rocks, about thirty feet thick. 
They are siliceous and argillaceous, decompose rapidly, are 
overlaid by heavy beds of dark red clay, containing large num- 
bers of silicified fossils and some nodules of chert. The best 
section seen of these rocks occurs along the line of the Cincin- 
nati Southern R. R., where they are exposed in a cut nearly 
three miles south of High Bridge. Just beyond the cut, on the 
east side of the track, the overlying clay has been scraped away 
to use in filling. The rugged rocks are here exposed in places 
