118 GEOLOGY OF THE TmRD DISTRICT. 



The Pentamerus limestone enters from the first district with considerable thickness, and 

 continues to the falls of Oneida creek, beyond which it was not distinctly recognized. Nor 

 is there any chance for its existence from the west end of Madison county, to Cayuga lake ; 

 for from thence the water-lime group, the Oriskany sandstone, and the Onondaga limestone 

 come together, to the exclusion of all the rocks intermediate to the water-lime group and the 

 Oriskany sandstone which Eire found at the east. It is rarely pure, being more or less 

 mixed with black shale, which gives a dark color to the rock, being usually a black grey. In 

 grain it is crystalline. It is in layers, but the lines of division arc not straight, and the sur- 

 face not even. The whole mass has a rough appearance ; it does not make a good building 

 stone, unless for cellar walls or field enclosures, owing to its accretionary character. Carbo- 

 nate of iron of a deep orange or brown color, but in very small quantity, is frequently seen in 

 this rock. From observations at the hill south of Sharon springs in the first district, from the 

 hill at the north end of Cherry- Valley, and from the road from Cooperstown to Fort-Plain, 

 there are three divisions in this mass according to the fossil character. In the descending 

 order, there are first, some layers with nodules of flint, the nodules not constant ; below 

 which, a series with the Galeated pentamerus in considerable number, with some other fossils, 

 such as the Deep euomphalus, (No. 2 of the wood-cut) ; under these, another series with 

 Gebhard's lepocrinites ; and then a third, with the Galeated pentamerus, showing a separa- 

 tion of the pentamerus layers by the Lepocrinites gebhardi. At Schoharie the two lower 

 divisions only exist, making the middle one the line between the pentamerus rock and the 

 succeeding one ; for which reason the above detail is given. 



The Galeated pentamerus and Gebhard's lepocrinites are in very great abundance ; their 

 fixed position, appearing with this limestone and disappearing totally with it, would be a great 

 marvel, if geology did not consist in great part of a series of such marvels. 



The pentamerus limestone may be seen south of Mr. Cruger's in the town of Warren, rest- 

 ing upon a mottled brown and blackish limestone full of columnariae, which, so far as I am 

 able to judge firom the specimens collected, do not differ in their internal structure from those 

 at the base of the group. No other rock is visible at the place, all being hidden by soil. 

 The water-lime group, however, is in the same hill-side to the east and north, at a lower 

 level. 



North of the village of Cherry- Valley, the pentamerus limestone may be seen in many 

 points. It forms the head of the falls at Judd's mill, and is uncovered for some distance on 

 the road to Fort-Plain. From its hardness, it often appears forming the hill-side through the 

 north part of Otsego, and is the surface rock in the towns of Stark, Warren and Columbia in 

 Herkimer county ; the pentamerus shells being very abundant in Herkimer, the most perfect 

 being found about two miles from Petrie's comers on the road to Cedarville. From Herki- 

 mer to Casety hollow they are rare, but reappear again in the ridge descending by the road 

 from Augusta village to Munsville. The last place where they were found with certainty, 

 was at the falls of Oneida creek below Foster's mill, the rock terminating before reaching the 

 longitude of Chiltcnango village. 



