TRENTON LIMESTONE. 303 



acter. At the quarry just east of his house, the rock consists of thick bedded, light 

 greenish blue, or gray limestone containing some argillaceous material distributed 

 through the mass in thin leaves, forming a rock quite similar to that which prevails in 

 the bed of the Lower Fox river. Between the heavy beds are greenish blue argilla- 

 ceous shales containing fossils, the small Brachiopods of the Blue beds predominating. 



Opposite this, on the south, a few feet of rock of a similar nature but more fossilifer- 

 ous, are underlaid by a partially exposed bed of dark blue crystalline rock. About forty 

 rods west of this is another shallow quarry displaying apparently a lower horizon. The 

 mass of the rock here has a rather brittle, compact, crystalline texture of dark, slightly 

 bluish gray color, and irregular or sometimes vitreous or conchoidal fracture. In tho 

 lower strata there is much chert, distributed in layers of nodules which are white or flint 

 colored and fossiliferous. The rock also contains frequent small geodes, the cavities be- 

 ing lined with calcite and occasionally pyrite, or rarely by zinc blende. The walls of 

 fissures are also sometimes lined with calcite and pyrite. A short distance to the nortli- 

 vrest of the quarry first mentioned the beds present the more usual characteristics of the 

 argillaceous portions of the Blue limestone as seen farther south. The strata at these 

 several quarries dip at an angle of about 2 to the southeast. 



Passing on to the north about ten miles we find in the S. E. qr. of section 28 of the 

 town of Center, a partially exposed low dome of rock, reminding us forcibly of the 

 Lower Magnesian mounds previously described, the more so because that formation lies 

 about two miles distant. The beds are exposed on the east and south sides, in which 

 directions they dip, but it is not certain that the uncovering of the other sides would bear 

 out the impression of a mound with quaquaversal dip, jjiven by an approach from the 

 east and south. It may be here remarked that the dip of the Trenton in this region is 

 greater and more varying than in the southern part of the state, though even here the 

 inclination rarely exceeds 7* or 8. The rock at this point is a bluish gray argillaceous 

 limestone, with shaly partings and very fossiliferous, the following species, many of 

 them represented by a large number of individuals, being gathered by the writer in a 

 half hour: Buthotrephis siicculens, Spongoid bodies Astylospongia? anew species of 

 Chcetetes, C. discoideus, Streptelasma corniculum, Schizocrinus nodosus, a new species of 

 Stictopora, Orthis lynx, 0. subquadrata, 0. testudinaria, a new species of Orthis, Strep- 

 iorhynchus, Strophoinena alternata, Leptcena sericea, Zygospira recurvirostra, a new 

 species of Rhynchonella, Raphistoma lenticularis, an undetermined cast of Murchisonia, 

 containing a fragment of Subulites, resembling S. brevis, Bellerphon bilobatus, Buca- 

 nia (fragment), Orthoceras and Illcenus taurus. 



In describing the Lower Magnesian limestone in the region just west of the last local- 

 ity, its relations to the Trenton were dwelt upon, and in view of that relationship, it may 

 be profitable to here record the occurrence of the following species in Sees. 25 and 26, 

 town of Ellingtou, immediately over against the escarpment of Lower Magnesian Mine- 

 stone: Paleophycus c&spitosum, Schizocrinus nodosus, Orthis lynx, Streptorhynchus 

 deflectum, Strophomena alternata, S. incrassata and an undetermined species of Khyn- 

 chonella. 



By reference to the maps it will be seen that the formation passes north through the 

 townships' of Freedom, Osborn, Seymour, Maple Grove, Lesser, Angelica, Little Suam- 

 ico, Pensaukee, Stiles, Oconto, Peshtigo and Marinette, as those townships are now con- 

 stituted. The exposures in these towns are scattered and meager, and represent chiefly 

 the lower member of the formation. They possess much local value as a source oi 

 building material, but in their present undeveloped condition they add but little of 

 knowledge or interest to what has already been said, although they indicate that the 

 characteristic peculiarities of the formation at the south undergo something of modi- 

 fication. 



It is the barrier interposed by this formation, that causes the Peshtigo river to make 



