48 LOWER PENINSULA. 



The fossils found at Stony Point, south of Alpena, are mostly 

 identical with the fossils found in the Thunder Bay Island strata, 

 but I believe the latter to be of a lower position than the first. 

 The fauna of the Hamilton group remains through the whole 

 period essentially the same, and a repetition of fossiliferous rock 

 beds containing the same species in different horizons is a fre- 

 quently observed fact. The position of the strata of Thunder Bay 

 Island is below that of the shale beds in Thunder Bay River near 

 Trowbridge's mills. The road from Alpena to Long Lake passes 

 the lime-kilns of Phelps, where a whitish brecciated limestone forms 

 the nucleus of several bubble-like hillocks ; the same limestone is 

 noticed resting on the shales of Trowbridge's mills. In going 

 north from Phelps's quarries, the surface rock retains the same char- 

 acter for several miles, the various beds which happen to be expos- 

 ed being sometimes fossiliferous, at other times not, while in places 

 layers are filled with hornstone concretions. Two miles south of 

 Long Lake, we come upon black, shaly limestones containing Atrypa 

 reticularis, Spirigera concentrica, Strophodonta demissa, Stropho- 

 donta erratica, Pentamerus papilionensis, Spirifer granuliferous, Cyr- 

 tina Hamiltonensis, Cyrtina umbonata, and Terebratula Linklseni, 

 besides corals and Bryozoa. These beds evidently underlie the 

 others. We find the black, shaly limestone continued from there as 

 the highest stratum on the hilltops bordering Long Lake, which 

 have an elevation of about 75 feet above its level. Descending to 

 the lake, underneath the black strata, gray limestones are found, 

 inclosing a few specimens of Stromatopora, Favosites, Atrypa reti- 

 cularis, Spirifer granuliferous. Lower beds are a coarsely crys- 

 talline, crinoidal limestone, and the base of the hillsides, to within 

 about 30 feet of the water level, is formed by an alternation of 

 shales, nodular seams of limestone, and some heavier massive lime- 

 stone ledges, all of which contain an abundance of specimens of 

 several species of fossils. The fossils are partly in silicified condi- 

 tion. The following is a list of the collected specimens: Stromato- 

 pora Wortheni, Stromatopora monticulifera, Cystiphyllum America- 

 num, Cyathophyllum profundum, Cyathophyllum scyphus, Favo- 

 sites Hamiltonensis, Favos. digitatus, Cladopora, Syringopora, vari- 

 ous Bryozoa, Atrypa reticularis, Spirifer mucronatus, Spirifer granuli- 

 ferous, Cyrtina Hamiltonensis, Cyrtina umbonata, OrthisTulliensis, 

 Spirigera concentrica, Terebratula Linklaeni, Pentamerus costatus. 



