WITH THOSE OF NEW YORK. 277 



occurrence of a thick and extensive mass of conglomerate, which 

 succeeds the Hudson river rocks in New York, These sugges- 

 tions are offered, not with any view to merge in one formation 

 what can be considered as decidedly distinct, but with the desire 

 to offer some facts toward the foundation of general groups or 

 classes, to which all the numerous minor subdivisions may be 

 referred. 



The junction of this group with the cliff limestone cannot be 

 seen in the neighborhood of Cincinnati ; but in passing down 

 the river, the two appear in juxtaposition before reaching Madi- 

 son, Indiana. In the Ohio Reports, Dr. Locke ^refers to this 

 place as exhibiting, in a very perfect manner, the contact of the 

 two rocks, cliff and blue limestones, which are well seen in the 

 deep cutting for the rail-road one mile southwest of the viUage, 

 and in a ravine still further below. 



The fossils of the blue limestone at this place illustrate the 

 same view as at Maysville and Cincinnati. The Plerinea cari- 

 nata, with one or two species of Cijpricardia, are common, while 

 Strophomena, Or this, and others, abound in the middle portions, 

 together with the Atrypa capax of Conrad, a species not seen at 

 Cincinnati. Large numbers of Cyathophylli occur, of a species 

 different from any in the higher rocks. Near the junction of the 

 blue and cliff, which latter is strongly contrasted in color, as well 

 as other characters, there occurs a stratum of twenty-five feet 

 thickness, of a greenish gray sandy shale, containing Ci/pricardia 

 modiolaris, and numerous spherical masses of coral, (Pontes,) 

 which lie in two courses, or ranges, near the top of the mass, and 

 separated by a few feet of shale from each other. Some of these 

 masses attain a large size, being three or four feet in diameter, 

 while others are but a few inches. 



The lower member of the cliff limestone at this place is a cal- 

 careo-siliceous mass, with green sti'ipes and spots, and crumbling 

 on exposure to the air. It appears quite destitute of fossils, so 

 far as I could discover. About fifty or sixty feet above the base 

 of this mass, I noticed a strong ferruginous exudation; but the 

 point being at the junction of the rock with the loose materials 

 above, I was unable to discover any ore in place. It is possible 



