312 Ulrich on Correlation oj the Lower Silurian. 
interstincta are two interesting bryozoa which occur at this 
horizon more frequently than at any other known to me. 
At ten feet above the base (/. <?, sixty feet above low water 
mark in the Ohio river at Cincinnati ) I have in several instances 
found a thin layer which is remarkable because it contains, be- 
sides large numbers of that small shell Leptobolus insignis.^ a 
number of fossils which are otherwise known only from the 
shale beds that have been described as occurring under the river 
bank in the first ward of Cincinnati. These fossils are Mero- 
crimis curtzis., Leptcena ■plicatella^ Triarthi^us becki., Pri?nitia 
bivertex and CyiJieropsis 7inicornis. The same layer is appar- 
ently represented in Taylor's creek east of Newport, Ky., 
where it is also about sixty feet above the bed of the Ohio river. 
The five species above mentioned ought perhaps to be counted 
as common to XI« and XI(^, but as they are characteristic fossils 
of the former and as none of them are known to extend higher 
in the series than stated, they have not been so regarded, but 
in the list are noted as restricted to the lower sub-division. 
In the succeeding twenty feet very few fossils excepting 
trails, tracks and so-called fucoids, occur. The latter, however, 
are moderately abundant and better preserved than at any sub- 
sequent horizon in the Lower Silurian strata under discussion. 
At about eightv feet above low water mark' (thirty feet above 
the top of XI<^) fossils once more become abundant, bryozoa 
being predominant here as they are at all subsequent fossilifer- 
ous horizons in the sub-division. From here on to ^ So feet 
above the river, fossils of that class increase in number until 
from the last mentioned level to twenty feet above they may 
be said to literally fill the shales. Where these layers are ex- 
posed to the weather the surface of the ground is found thickly 
strewn with generally w^ell preserved fragments. These belong 
to many species, but as by far the most of them belong to three 
species of Dekavella (/?. ulrichi^ D. obsc7ira., D. n. sp.) the 
layers might be appropriately called the Dckayella bed. Orthis 
fnultisecta., Mo}wtrypella cequalis^ Batostoma jaijtesi., B. ifnpli- 
cata., Callopora sig-illaroidca., Ceramoporclla distiucta^ C. ohio- 
1 When this expression is used, without being otherwise qualified, it 
refers to low water mark in the Ohio river at Cincinnati, O. 
