166 INDEX TO THE STRATIGEAPHY OF NORTH AMERICA. 



underlying limestone layers and exhibits other evidences of unconformity by 

 erosion" with the overlying shales. In the report just cited the authors state: 



The strata of the Cincinnati period as exposed in Ohio, Indiana, and Kentucky are divisible 

 into three groups, having about the same geological value as the Chazy, Stones River, Black 

 River, and Trenton groups of the Trenton period and the Medina, Clinton and Niagara groups 

 of the Niagara period. These three divisions correspond very nearly with the Lower, Middle, 

 and Upper Hudson of the Kentucky geologists, and the Eden shales, Hill Quarry beds, and 

 Lebanon beds of Prof. Edward Orton in volume 1, Geology of Ohio. 



At Cincinnati we begin the period with the Utica group, which here consists of over 250 

 feet of grayish and blue calcareous shales and marls, in which many layers of more or less 

 crystalline limestone, from 1 to 20 inches thick, are included. The lower 14 or 20 feet of this 

 division are of a darker color than the succeeding shales, being greenish gray or drab rather 

 than light blue. 



It is this portion that agrees best in all respects with the Utica of New York and Canada, 

 and it was so determined by Prof. James Hall as early as 1842. The gray shales contain more 

 or less abundantly such widely distributed and characteristic Utica fossils as Triarfhrus iecki, 

 PrimitieUa unicornis, Leptoiolus insignia, Lingula daphne, DicranograptiiS ramosus, Diplograptus 

 spinulosus, D. putiUus, Dendrograptus simplex, and D. tenuiramosus. Of these, the last three, 

 as well as many other species, continue into the main body of the shaly strata of the group. 

 Throughout, fossils, Bryozoa especially, occur in greater abundance, variety, and perfection 

 than at any other known locality for the Utica. At the top the shales pass rather gradually 

 into the "Hill Quarry beds." 



The latter, for which we propose to use the name Lorraine group, are clearly equivalent to 

 the greater part of the New York strata which Emmons included under that name." At the 

 base of the division, which at Cincinnati comprises about 200 feet of strata, there are some 

 arenaceous layers that on weathering frequently preserve the fossils as casts. Above these 

 there are numerous layers of crystalline limestone, 3 to 10 inches in thickness, separated by 

 relatively thin bands of shale. In the upper 60 or 70 feet the bedding is more irregular and the 

 limestone layers thinner and generally argillaceous, unfitting them for building purposes. 

 Fossils are weU preserved and exceedingly plentiful and among them may be recognized nearly 

 every species that has been described from the equivalent beds in New York. Perhaps 300 

 species of fossils are known from the Cincinnati exposure of the Lorraine group and of these at 

 least two-thirds are limited to the group, which is, considering the very similar lithological 

 characters of the preceding and succeeding beds, a surprisingly large percentage. 



Resting on the Lorraine there is a series of alternating thin-bedded shales and limestones 

 and in some localities finally a sandstone, in all quite 350 feet thick in southwestern Ohio and 

 southeastern Indiana. Almost the entire series is excellently exposed at Richmond Ind. so 

 that the name Richmond group which we propose to apply to the series is eminently appropriate. 

 East and southeast of Oxford in Ohio the whole group consists of thin-bedded limestones and 

 shales, but at Richmond the upper part shows an increase of arenaceous matter while the upper- 

 most layers of shale have become harder and include one or two heavy beds of impure limestone. 

 Southward from this locality in Ripley and Jefferson counties, Ind., the heavy layers are 

 increased. In the last county their texture is very compact and the color a drab or dove 

 reminding one in both respects very greatly of some beds of the Trenton period. In Indiana 

 and Ohio this upper part of the group is, as a rule, not very fossiliferous, but when the bed is 

 traced over into Kentucky it becomes a veritable coral reef reaching from Jefferson County, Ky., 

 to and beyond Marion County. The rock in this distance has changed some, being in the last 

 county of a yellowish color and finely arenaceous texture, the whole giving way very readily 

 under the weather so that the surface is sometimes thickly strewn with masses of Columnaria 

 Tetradium, Labechia, and Beatricea. 



a We refer particularly to Emmons's Lorraine sandstone, the greater part, if not all, of his Lorraine shales, which 

 Walcott in 1879 referred to the Utica, being probably equivalent to the upper part of the Utica at Cincinnati.' 



