42 



LOWER PENINSULA. 



the bluffs are hidden from view ; between the next point north- 

 ward, Stony Point, and Partridge Point, a low, swampy spa.ce 

 about a mile in width extends, on which no rock ledges can be 

 seen ; it is, however, evident, from the strike and dip of the strata, 

 that the beds composing Stony Point are below those of Par- 

 tridge Point, and that no great mass of rock strata can intervene 

 between them. The ledges of Stony Point are first noticed 

 submerged, while northward, by a gradual rise of the strata, they 

 project about three or four feet above the water level. They are a 

 light-colored limestone, full of large convex masses of various species 

 of Stromatopora, particularly Str, monticulifera and Str. Wortheni, 

 Some deeper ledges of darker color and of a nodular structure, 

 with intermingled shaly seams, are rich in many species of fossils, 

 chiefly Cyathophyllum Houghtoni, Cyathophyllum Hallii, Cysti- 

 phyllum Americanum, Diphyphyllum Archiaci, Cyathophyllum pro- 

 fundum, Favosites Hamiltonensis, Favosites nitella. Alveolites 

 subramosus, various forms of Syringopora and of Aulopora, and 

 numerous Bryozoa. Of Brachiopods, I may mention Atrypa reti- 

 cularis, Spirigera concentrica, Spirifer mucronatus, Spirifer zigzag, 

 Cyrtina Hamiltonensis, Pentamerus aratus, Strophodonta demissa, 

 Strophodonta erratica. Crania Hamiltoniae, Crania crenistria, with 

 a number of others. 



Analogous rock beds form the surface rock over an extended 

 space west and northwest from Stony Point. The hillsides lin 

 ing the south side of Thunder Bay River, in Sections 28 and 20 

 of Alpena town, present a number of exposures of the strata 

 in question. The highest beds seen in these localities are light- 

 colored limestones containing few fossils beyond some Crinoid 

 stems and ramulets of Bryozoa. Under them follow nodular 

 limestones abounding in irregular, flexuous seams of black bitu- 

 minous shale matter. The mass of these limestones is almost 

 entirely composed of different species of Stromatopora, Favosites 

 Hamiltonensis, Cyathophyllum profundum, Cyath. Houghtoni, 

 etc. Somewhat lower strata are of a lighter blue or drab color, 

 with the shaly seams very prevalent throughout the ledges. They 

 are very fossiliferous, containing about the same forms as have 

 been enumerated as belonging to the lower beds of Stony 

 Point, besides a few others not seen there, as Cystiphyllum 

 aggregatum, and large lumps of Chaetetes and of a Fistulipora 



