RAYMOND: CORRELATION OF THE ORDOVICIAN STRATA. 259 
horizon, most of them passing up through the Perrys- 
ville. Three species of Fusispira, and other gastropods 
are present. Wilmore formation. 70 
2. Fine-grained limestone alternating with clayey layers of 
similar thickness. Heterorthis clytie, Dalmanella fertilis, 
Leptaena tenucstriata, and Cryptolithus tessellatus are char- 
acteristic species. Hermitage formation. 22 
1. Granular limestone with cystids, Edrioaster bigsbyz, Orthis 
tricenaria, Dinorthis pectinella, ete. Curdsville formation. 23 
On a first survey of the lithological characteristics of the section 
in central Kentucky, one is impressed by the large amount of light- 
colored, fine-grained and coarse-grained rather pure limestone and 
the lack of dark-colored shale. 
Columnaria occurs in the Curdsville, Flanagan, and Cynthiana 
formations, and Tetradium in the Hermitage, Perrysville, and Cyn- 
thiana, so that the Wilmore and Benson are the only formations 
without corals. 
Because of the presence of species of Amygdalocystites, Pleuro- 
cystites, and Edrioaster in the Curdsville in Kentucky it has become 
the custom to correlate this zone with the cystid zone of Ontario. 
Ulrich, and following him, Bassler, have correlated the Prosser of 
Minnesota with the Curdsville of Kentucky, a correlation not borne 
out, I think, by the evidence. 
The Curdsville fauna of Kentucky is a pure derivative of the Black 
River, only the echinoderm fauna being added to a rather typical 
Leray-Black River assemblage of fossils. 
In Minnesota the Pleurocystites occur in a very. different associa- 
tion. They are found in the lower part of the Fusispira beds (zone 7 
of the section above) where they are associated with Strophomena 
trilobata, Cyclospira bisulcata, and Rafinesquina deltoidea, all Upper 
Trenton species in New York and species which are never found so 
low as the Black River. This zone is also above the Clitambonites 
bed, which can not be correlated with anything older than the Wilmore 
of Kentucky. 
In Ontario there are three “Curdsville”’ zones, two above and one 
below the bed which is correlated with the Clitambonites bed of 
Minnesota. All are seen in the section at Ottawa, where the zones 
are separated by seventy-five feet of strata containing two distinct 
faunules. 
The lower zone, to which I have given the formation name Hull, is 
