Review of the New York Geological Reports. 65 
points of difference, and, if you please for your own convenience 
and for the sake of classification, to give provisional names to 
those apparently distinct ; but we feel convinced that just in pro- 
portion as the collection is extensive and the comparison of forms 
critically traced, the tendency of maturer reflection will be to cur- 
tail the number of species. We have been forcibly struck with 
this fact in our investigations into the specific character of those 
western paleozoic forms which occur, in certain localities, in 
such vast profusion. 
The diversity of outline which the D. mucronata assumes, 
seems to be caused by a variation in the lithological character 
of the sedimentary deposits, as appears from the following re- 
marks :—“ This very ornamental shell and its numerous varieties 
in form are very interesting. In the soft calcareous shales of 
western New York, it is shorter and more rotund; while in the 
sandy shales and shaly sandstones of the middle and eastern part 
of the state it is greatly extended and its extremities very acute.” 
Calymene bufo, fig. 6 of the preceding cut, is an abundant and 
well known fossil of the shale strata on the Falls of the Ohio. 
It occurs also in the limestone of Red Cedar and the Wapsenonox 
in the Du Buque district of Iowa. 
Hall remarks on fig. 4, Strophomena inequistriata of Conrad: 
“'There seems to me good reason for considering this form and 
S. mucronata of Conrad as identical, and that both are identical 
bag Orthis interstrialis.. (Phil. Paleozoic Fossils, plate 25, 
g. 103.)" ts a: 
“In the calcareous shales of the Hamilton group, its form is 
often better defined and more rotund, though the strie are less 
sharp ; while in the Chemung rocks, it is usually compressed, and 
very frequently the shell is partially or entirely removed.” 
Fig. 8, L i nexilis is believed to be the same as fig. 
183, pl. 38, Phil. Paleozoic Fossils, and Terebra nexilis of 
Sowerby, fig. 17, pl. 54, volume v, Second Series, is given as a 
synonym. ae 
district. ; : heidi tam i+ 
The species of Delthyris considered by Hall as most character- 
isti in his Report, are embraced in the 
istic, and represented in ort, are em in the two 
wood-cuts on the following pages. 
_ At Charleston, Clark county, Indiana, an extension of the 
shell beds of the Falls of the Ohio contains a Delt/ aving a 
* macronota, fig. ‘ , : 
of the western fossil is not quite so narrow, the concentric 
Szconp Sznizs, Vol. III, No. 7.—Jan., 1847. 9 
