i 
Or 
2 PROCEEDINGS OF THE GEOLOGICAL society. [Dec. 1, 
Wenlock beds. Nevertheless, although it may contain a few Upper 
Silurian species, I think that Mr. Hall has classed it correctly in the 
Lower Silurian series, which must be taken as ending with the 
Clinton group. 
It is not so easy to state the correct place of the Cliff limestone of 
Ohio, as it appears from Mr. Hall’s Report, p. 519, and from M. 
de Verneuil’s remarks in the Bulletin of the Geological Society of 
France, vol. iv. p. 12, that the western geologists have thrown together 
under this name calcareous beds containing both Silurian and Devo- 
nian strata. I hope that M. de Verneuil may give us some further 
remarks on this subject, which is at present in great obscurity*, 
6. Niagara Shale and Limestone. 
These two beds so closely resemble the limestone and shale of 
Dudley, both in mineral character and in organic remains, that they 
have been regarded as their exact equivalents: this however is carry- 
ing the comparison too far, as it will soon be shown that many of the 
limestones of the Helderberg series must also be included in the 
Wenlock formation. 
The shells im these beds belong mostly to the Brachiopoda, and 
the number of species identical with those found in the Wenlock 
rocks in this country is very remarkable; while none are species 
found in England exclusively in the Lower Silurian formation. The 
following are seen in Mr. Lyell’s cabinet :-— 
Atrypa didyma ? Spirifer plicatus. 
Leptzna depressa. radiatus. 
transversalis. Strophomena grandis. 
Orthis elegantula. Terebratula cuneata. 
Spirifer crispus. reticularis. 
To which may be added, on Mr. Hall’s authority,— 
Orthis hybrida. Strophomena pecten. 
Spirifer biloba. 
7. Onondaga Salt Group. 
Water-lime Group. 
The first of these is a deposit of great extent and thickness, and of 
great economical importance from its supply of salt and gypsum: the 
next forms a passage from the Salt group to the calcareous system 
above. Both beds contain few organic remains; the only European 
species I have seen is the Spirifer plicatus. 
8. Pentamerus Limestone. 
Delthyris shaly Inmestone. 
Encrinal Limestone. 
Upper Pentamerus Limestone. 
These four beds form a calcareous series so closely connected in 
* These anticipations have been fully realized by the publication of M. de Ver- 
neuil’s views on the subject in the ‘ Bulletin de la Société Géologique de France,’ 
t. iv. p. 646. 
Soo Oe eee er eT eS ee 
