572 AxNALS OF THE Carxegie Museum. 



St. Paul, Minn., occurs at two horizons, one near the middle of the 

 formation, and the other near the top. 



James correlated the St. Peter on lithological grounds with the 

 Chazy of the Ottawa Valley, Init there are no species common to the 

 two formations, and lithological characters signify little when the 

 faunas can be compared. 



From the close relationship of the St. Peter fauna to that of the Mo- 

 hawkian, it seems probable that this formation was deposited during 

 Stones River time. 



Stones River Group. — In the Columbia folio of the United States 

 Geologic Atlas, Ulrich has correlated in time the lower part of the 

 Stones River Group, including the Lebanon, Ridley, Pierce and Mur- 

 freesboro limestones, with the Chazy of New York. This correlation 

 is evidently based mainly on stratigraphic grounds, as Ulrich and 

 Schuchert in their article on Paleozoic Seas and Barriers, have held 

 that the Lowville of New York is the northeastern representative of 

 " the extreme top of the Stones River " Group. 



In the Columbia folio referred to above, Ulrich has tabulated the 

 fossils of all the divisions of the Stones River Group, as developed in 

 the middle Tennessee region. In the Lebanon limestone, the upper 

 member of the Stones River Grouy) which is there correlated with the 

 Chazy, there are, according to the table, 37 species, beside ten un- 

 described Bryozoa. Of these 37 species, seven are Bryozoa and five 

 are not specifically identified. This large number of Bryozoa, 17 

 species, would at once suggest that the formation which contained them 

 is much more closely allied to the Trenton than to the Chazy. Leav- 

 ing out of account the Bryozoa, which, in the Ordovician, nearly 

 always have a very restricted range, and the five forms not specifically 

 identified, it is found that seventeen of the twenty-five species remain- 

 ing are Black River or Trenton forms. All the brachiopods, four of 

 the five gastropods, and two of the three trilobites are species found 

 in higher formations. Even if all the described species be included, 

 53 per cent, of the species of the Lebanon limestone are Mohawkian 

 forms. 



Below the Lebanon is the Ridley limestone, about 80 feet in thick- 

 ness. Of the nine species listed from this horizon, six are found in 

 the Black River. 



Below the Ridley is the thin Pierce limestone with twelve species 

 listed, and twenty undescribed bryozoans. Only eleven forms are 



