26 BULLETIISr 11, UNITED STATES NATIONAL MUSEUM. 



Ordo vician — Continued . 



Black River group — Continued. 



Decorah shale — Continued. Feet, 



(e) Gray, greenish or blue shale with nodular gray limestone in 

 the upper part and knotty, calcareous masses in the re- 

 mainder. (Fucoid bed.) Dinorthis pectinella and Camaro- 

 cladia rugosa abundant, but other fossils are rare and are of 



species found in the underlying bed 0-10 



(d) Blue shale weathering greenish gray, with fossiliferous, even or 

 knotty plates of limestone. Fossils abundant. (Phyllopo- 



rina bed.) 10-15 



(c) Green to blue shales with numerous bryozoans and moUusca. 



(Ctenodontabed.) 0-10 



(6) Greenish blue shale with a few thin plates of limestone. 



Fossils numerous, chiefly bryozoans. (Rhinidictya bed.). . 0-34 

 (fl) Soft green shales and irregular layers of limestone with numer- 

 ous fossils, particularly bryozoans. (Stictoporella bed.) 3-10 



Platteville limestone (Lowville age) — 



(6) Blue to gray fine-grained dolomite weathering brownish to 

 yellow. Fossils occurring as c'asts, numerous in certain 



layers. (Vanuxemia bed .) 0-12 



(a) Thin bedded, fine-grained, locally somewhat argillaceous 



limestone, often cobbly or shaly toward the base 15-28 



Stones River group — 



"Lower Buff" dolomite — 



Bluish gray dolomite, weathering grayish buff, more or less cellu- 

 lose, usually thick bedded in the middle part, thin and impure 

 above, and sometimes conglomeratic and sandy at the base. 



Fossils few 6-13 



Glenwood shales — 



Soft green shale or clay, the lower part of a rusty color, and com- 

 monly with grains of quartz sand derived from the underlying 



St. Peter 1-6 



St. Peter sandstone — 



STONES RIVER GROUP. 



The best development of this group is in its type-locality, central 

 Tennessee, where its several formations are quite fossiliferous. Each 

 of the Stones River faunas seems to be of southern origin and to have 

 little in common with those of the Black River. With the exception 

 of one or two species of the long-lived Corynotrypa, not a single 

 bryozoan of the many known Stones River forms is strictly identical 

 with any in the Black River group or in the Baltic Ordovician. The 

 few fossils found in the St. Peter sandstone, Glenwood shale, and 

 "Lower Buff" dolomite, comprising the Stones River of the Minne- 

 sota-Iowa basin of deposition, likewise have little relationship to the 

 faunas of later times and need not be mentioned further. A con- 

 siderable number of species has been recorded from the "Lower 

 Buff" dolomite, but, almost without exception, these belong to the 

 lower members of the Platteville limestone described later. 



