CARBONIFEROUS LIMESTONE. 103 



served in the vicinity of Caseville, on the farm of Mr. Klump, in 

 Town. 18, Range 11, Sect. 18, where bluish drab-colored limestone 

 beds of dolomitic, or partly of arenaceous character, repose on the 

 upper coarse-grained sand-rock ledges of the Waverly group, similar 

 to those exposed some miles east of the place, at Hat Point. 



The limestones contain a species of Productus with very convex 

 ventral valve, shallow, sinuated in the median line, and covered by 

 from 40 to 50 fine sub-equal ribs, a Retzia similar to Retzia vera 

 Hall, Terebratula (similar to Eudora), Spirifer Marionensis, and 

 Spiriferina spinosa. At Oak Point, a short distance north of the local- 

 ity just mentioned, fragments of similar fossiliferous, arenaceous lime 

 rock are thrown out by the lake, and in its bottom, a short distance 

 off shore, larger angular blocks of the same are found. Some of the 

 slabs thrown ashore are almost totally composed of fragments of 

 Brachiopod shells, besides other bivalves, Crinoid joints, stems of 

 Bryozoa, etc. In dredging out the harbor at Caseville, rounded, 

 strongly drift-worn limestone boulders of the same lithological 

 character, and inclosing similar fossils, are brought up with the 

 mud masses ; among them are dark, bluish-colored, fine-grained 

 limestones, crowded with shells of Lamellibranches, Myalina, 

 Modiolopsis, Schizodus, with some Brachiopods, Rhynchonella, Ret- 

 zia, Terebratula, etc., intermingled. Other calcareous rock bould- 

 ers are of a slaty, laminated structure, of a dark, nearly black color, 

 and filled with band-like, compressed stems, divided by regular con- 

 strictions into suborbicular segments. The bands seem originally 

 to have been hollow utricules, with veinous, longitudinal carinae ; 

 their substance is brownish, horn-like, and semi-translucid ; most 

 probably they are vegetable organisms. Other palaeontologists to 

 whom I showed the specimens suggest that they are related to 

 Graptolites. A short time after I found these slaty boulders, 

 whose position was not known to me, I discovered in the bed of 

 Rifle River, at Island Rapids, Town. 21, R. 3, Sect. 28, the same 

 rock in place ; besides the stems mentioned, it contains a Productus 

 and some shells resembling Modiolopsis. It forms the lowest beds 

 in the rapids, visible to a thickness of 3 or 4 feet ; above them are 

 from 6 to 8 feet of limestones, of crystalline structure and dark gray 

 color, full of Crinoid joints and shells or their fragments. Among 

 them I recognized a large Aviculopecten, a Rhynchonella, Spiri- 

 ferina spinosa, Productus, and quite numerous specimens of an 



