LOWER MAGNESIAN LIMESTONE. 283 



7. A yellowish or grayish dolomite of very rough, irregular, granular crystalline and 

 earthy texture, containing geodes and almost devoid of bedding lines. 6 feet. 



S. At the base of the above, are two thin layers that present a virescent hue, caused 

 by small green spherules imbedded in a gray rock. Associated with these are a greater 

 or less number of oolitic spherules, some ocherous, and others in which the center is yel- 

 low and the exterior green, which suggests that the coloring matter may be a ferrous 

 compound of iron which oxidizes to the hydrated ferric form. On the weathered portion 

 of the rock these little spherical bodies are wholly or partially dissolved out, giving a harsh, 

 minutely pitted surface. Those that are partially dissolved, show a radiating structure 

 somewhat resembling some of the Foraminifera, but the rays are not reducible to any 

 definite numerical system. Aggiegations of similar problematic forms, not green, but 

 usually white, occur in and upon the surface of the layers, disposed precisely as the 

 white oolitic masses are in the layers below, some of which show clearly a concretionary 

 structure, making it probable that all are so. They deserve more study than it has been 

 possible yet to give them. The same layers contain many illy preserved remains of 

 what appear to be an undescribed species of Salterella and also an undetermined Gas- 

 teropod having a low broad coil. The gray portion of the rock is a mixture of earthy 

 and crystalline granular material, rather soft, and has an easy regular fracture. 6 inches. 



9. This fossiliferous layer graduates below into a very peculiar dolomitic and silicious 

 rock, in which the concretionary structure attains an unusual development. Almost the 

 whole mass is formed of vanously sized concentric segregations of chtrt and dolomitic 

 material. They are not unfrequently two or three feet in diameter, and resemble coarse, 

 gigantic Stromatopora. 2.2 feet. 



10. This rests upon a dark gray dolomite, similar to that immediately above the con- 

 cretionary layer, but contains aggregated masses of white oolite, and is itself somewhat 

 oolitic from the presence of yellowish and dark gray spherules. The white ones are of 

 large size, and upon fracture and abrasion show their con centre structure. They are 

 aggregated so as to form flat or nodular masses similar to those usually assumed by chert 

 in this and the higher Silurian formations. 16 inches. 



11. Closely associated with this below is a layer of a pistachio-green cast formed by 

 abundant green spots, with which are mingled a less number of yellow, orange and red- 

 dish ones, the rock mass being gray. Aside from the colored spherules, it is slightly 

 oolitic and rather soft, possessing a regular easy fracture. The Salterella occurs here 

 also. ?> inches. 



12. The base of the exposure is formed by a dark gray, very impure, and for the most 

 part oolitic dolomite. The ooliths are generally darker than the mass of the rock, and 

 the larger ones are seldom perfectly spherical, but incline to the forms usually assumed 

 by chert nodules. Ocherous spherules occur, and occasionally red hematite ones. In 

 some layers, quartzose sand is abundant, forming seams or lenticular masses. Geodes, 

 both of quartz and calcite occur. The bedding is very irregular. 5 fe t. 



Total exposure. 53.2 feet. 



The falls have a vertical descent of 22 feet, with a fall of 10 feet on the rapids above, 

 and a greater amount balow. 



A few miles north of Stiles, on Jones creek, a thinner band of shale, very similar to 

 that described above, gives rise to a diminutive imitation of Oconto Falls, though the 

 layers are not specifically identifiable with those of the preceding section. The dip is 

 undulating, so that though shown for some distance along the stream, but a small verti- 

 cal thickness is exhibited. 



The upper portion of the formation is displayed at several points between Angelica 

 and the Oconto river; at Ordway's ledge and vicinity, about five miles north of Stiles; 

 and on the south side ot the main Peshtigo river, from above the mouth of the Little 

 river to near the bend above Potato rapids. At these several points the uneven nature 



