56 LOWER PENINSULA. 



bluffs are uncovered in the ditches of the road bed, and descending 

 at this point to Ingall's mill, situated about 40 feet lower, we find, 

 next under these ledges, hard, bluish-colored limestones contain- 

 ing Stromatopora monticulifera, Stromatopora Wortheni, and Cya- 

 thophyllum profundum. At Porter's old mill site, below the lime- 

 stones, 6 or 8 feet of blue shales come out in the bed of the creek, 

 filled with specimens of Cyathophyllum profundum, Favosites Ham- 

 iltonensis, Atrypa reticularis, Strophodonta erratica, etc. Then 

 follow limestones again, which form the bed of the creek down- 

 ward to the foot of the race at Ingall's mill, amounting to 

 about 20 feet in the outcrop. They contain nearly the same 

 fossils as the shale beds above. Following the bed of the creek 

 down to its mouth, rock ledges are again several times un- 

 covered, but their exact position with regard to the ledges of 

 the upper part of the section is not seen. The total descent which 

 the creek makes from the top of the railroad bridge to the lake 

 shore is 90 feet, all of which is made up by limestone beds, with 

 the exception of the mentioned seam of shales. About one mile 

 west of the mouth of Bear Creek, an ascending section through 

 the strata can be observed by following the lake shore westward, 

 commencing about at the bottom of the section given above. 

 The lowest ledges seen, partly submerged under water, are hard 

 blue limestones of rugose surface, and interlaminated with seams 

 of black bituminous shale. They contain Cyathophyllum profun- 

 dum, Stromatopora Wortheni, Stromatopora monticulifera, and 

 Atrypa reticularis. A few hundred steps farther, in a low bluff, 

 about 12 feet of the next higher ledges are seen resting on the 

 former ; they consist of light-colored, brittle limestones, of fine- 

 grained, conchoidal fracture, interstratified with calcareous shales. 

 In places, the rock beds contain only few fossils, while the same 

 strata may be crowded with them some steps farther on. The most 

 common forms inclosed are Cyathophyllum profundum, Cysti- 

 phyllum Americanum, Favosites Hamiltonensis, some Bryozoa, 

 Spirifer pennatus, Spirifer mucronatus, Cyrtina Hamiltonensis, Stro- 

 phodonta erratica, Strophodonta nacrea, Pentamerus papilionensis, 

 and Atrypa reticularis. The outcrops are then interrupted by a 

 high drift bluff which comes up to the shore ; at its foot sometimes 

 one of the ledges of the beds referred to sticks out. On the other 

 side of the drift bluff, which is only a few hundred yards wide. 



