TYPICAL TRENTON FOSSILS. -'505 



Camarella bemensis, Sardeson. 0. rogata, Sardeson. 



Q. hemiplicata, Hall. Streptorhynchus rhomboidalis, Wilck- 



C. owatonnensis, Sardeson. ens. 



Crania trentonensis (?), Hall. Strophomena minnesotensis (f), N. H. 



Distinct concordensis, Sardeson. Winchell. 



Leptsena minnesotensis, Sardeson. Zygospira recurvirostris, Hall. 



Lingulella iowensis, Owen. Bellerophon bilobatus, Sowerby. 



Orthis beUarugosa, Conrad. Fusispira elongata, Hall. 



f>. biforata, Schlotheim. i^. ventricosa, Hall. 



The Liiif/iila.snifi Bod. — This division is 20 feet thick, consisting of very 

 heavily bedded limestone and containing few fossils or impurities of any 

 kind. In places it is strikingly colored by infiltration bands. From 

 this appearance it is by quarrymen called a sandstone, although desti- 

 tute of quartz grains. It is an excellent building stone. In fossils it 

 carries — 



Distinct concordensis, Sardeson. 0. biforata, Schlotheim. 



Lingidasma schucherti (/), Ulrich. 0. rogata, Sardeson. 



Lingulella iowensis; Owen. Bucania punctifrons, Emmons. 

 Orthis beUarugosa, Conrad. 



The Mad it rat Bed. — This is a coarsely bedded limestone. In weather- 

 ing it passes into a coarse porous rock strongly resembling a sandstone 

 hi some respects; it develops a marked staining through the infiltration 

 of ferric oxide along its joints. Perpendicular bluffs exposing all or 

 nearly all of its thickness are quite common. 



Its fossils are few but. for the Minnesota Silurian, of unusually large 

 size. On account of their rarity they can be found only where large 

 quantities of rather fresh debris are accumulated in quarries and the 

 gorges of streams. These have been noted : 



Receptacidites oweni, Hall. Maclurea cuneata, Whitf. 



Fusispira elongata, Ball. .1/. major, Hall. 



/•'. ventricosa, 1 1 all. 



Till: CINCINNATI LIMESTONES AND SHALES. 



'lite Maquoketa Beds: Localities. — These beds are displayed at Granger, 

 three miles wesl of Forestville, and near Spring Valley ; everywhere in 

 small exposures. 



Structural Characters. — This is a heavily bedded crystalline Limestone 

 alternating with beds of shale. The limestone predominates in the Lower 

 layers and the shales in the upper. The shales may easily be mistaken 

 in Lithologic and structural characters for the Stictoporella bed of the 

 Trenton. The thickness of these rocks in the exposures \ Lsited is about 



