110 
[Assembly 
Producta ^sulcata, S. 
^hemispherica, S. 
scabriculaj S. 
*Euomphalus catillus, S. 
Goniatites Henslowi, S. 
minuta, S. 
Calamopora polymorpha, Goldfuss. 
Limestone containing these fossils is not of frequent occurrence in 
Pennsylvania or Ohio; the shells being chiefly embedded in bituminous 
shale and ironstone and, in Ohio, in chert. It is only west of the Mis- 
sissippi that the mountain limestone becomes an extensive and impor- 
tant rock. 
1. The first group of strata, in the descending order, below the sand- 
stone which contains impressions of terrestrial plants, consists of rocks 
which are seldom calcareous, and appear to be equivalent, as mentioned 
in my report of last year, to the Ludlow rocks of Murchison. In Mr. 
Vanuxem's report will be found an accurate account of the characteris- 
tic species of each group. 
Organic remains op the first group. 
Radiaria. European localities 
Cyathocrinites pinnatus, G Eifel. 
Euryale annulatum, Dekay. 
Testacea. 
Posidonia lirata, C. 
Pterinea fasciculata, G Nassau. 
concentrica, C. 
bisulcata, C. 
appressa, C. 
punctulata, C. 
cuneata, C. 
triqueter, C. 
Avicula tuberculata, C. 
Lima macroptera, C. 
Monotis princeps, C. 
Orbicula ovalis, C. 
Delthyris undulata, S Arran. 
macroptera, G Coblenz. 
inciUs, C. 
Producta spinulosa, S Lithlingow. 
