FRANKLIN COUNTY. 635 



One of the most conspicuous features of the Huron shale is found in 

 the concretions, great and small, which it contains in great numbers. 

 They begin with the formation, and in the lowermost forty feet, all the 

 varieties of their structure can be seen. The shape which the larger 

 and more symmetrical take is that of flattened spheroids. Not unfre- 

 quently two are joined together by a ligament, uniting their centers. 

 They are sometimes, but more rarely, disc-like, and many of them lack 

 regularity of outline. In composition, some variety is observable. Very 

 many of. the smaller ones consist of the crystallized bi-sulphide of iron, 

 and some of them consist of a symmetrical shell, or scale of this sub- 

 stance, around a softer nucleus, which gives them a strong resemblance 

 to an iron casting. The nodules of this kind are often irregular in shape. 

 The larger specimens invariably contain lime and iron, the former sub- 

 stance being sometimes found at the center, in the shape of cale spar, 

 but more frequently occurring in a dark, semi-crystalline mineral, that 

 is quite characteristic. The iron is always intimately associated with 

 the lime, and gives to the weathering concretions the dark yellow, or 

 ochreous color, that marks them all in this stage. 



Rarer substances sometimes are met in the crystalline nuclei of the 

 concretions. Heavy spar is one of these. As is now well known, there 

 are sometimes found at the centers of these bodies organic nuclei, and 

 among these, are some of the most interesting and remarkable fossils of 

 the entire geological series. Wood is not uncommon in this connection. 

 A species of ancient pine, Dadoxylon Newberryi, Dawson, furnished many 

 of these centers. 



The great fish bones, however, are the most remarkable forms to be met 

 with here. 



To Rev. H. Herzer, of Berea, Ohio, the credit is due of bringing to light, 

 by his very sagacious and patient labors, the bones of the most remark- 

 able of the great series of fossil fishes, that the rocks of Ohio have so far 

 yielded. 



Dinicthys, the fish to which reference is here made, is one of the re- 

 markable fishes of this early age of the world as well. It united, in a 

 surprising way, the characteristics of forms widely separated now. More 

 than any other fossil, it has served to show that the great group of Ganoids, 

 of Devonian time, to which group it belongs, " formed the parent stock 

 from which, by differentiation, the fishes have branched off on one side, 

 the amphibians and reptiles on another." It agrees so closely in denti- 

 tion with the modern Lepidosiren, which most systematists rank as the 

 highest of modern fishes, that the latter can scarcely be doubted to be 

 derived from it by lineal descent. There are two species of this genua 



