LOCAL GEOLOGY OF DAVEXPORT— BAKEIS. 263 



neighborhood of Moline and Rock Island, of which it is claimed they 

 form the upward extension ; to define the limits within which fossils are 

 found, and to call attention to a group of fossils which distinguish these 

 beds, and differ from any of the well defined fossils of the Hamilton. 



On the Iowa side of the river for some years, quarrying has been 

 carried on to such extent that new facts have been gradually accumu- 

 lating, bearing upon the subject. Examinations have been made from 

 time to time, such as seem to justify the writer in the views presented. 



In the locality described by Prof. Worthen — the quarries between Eock 

 Island and Moline— immediately below the well-known shales and 

 limestones of the Hamilton, occurs " a light bluish grey or dove colored 

 limestone, irregularly bedded and concretionary in structure, quite desti- 

 tute of fossils, except in its upper layers, near its juncture with the 

 shales, where it contains Phillipsastrea verneuili, Alveolites and Atrypa 

 reticularis.^'' The junction with the shales in some parts is so very grad- 

 ual that it is difficult to draw the line of separation. 



On the Iowa side the passage is distinct and abrupt. With the above 

 named fossils are associated on the surface of the ground huge masses 

 of Cyathophyllum coalitum. Favosites hemispherica, Cladapora Fisclieri., 

 with various species of Zajjiirentis, Alveolites aud Stromatopora, which, 

 though now detached from each other, at a distant day were no doubt 

 consolidated into a coral reef. Immediately underlying these, in each of 

 the three quarries below the city, are a series of rough, irregular beds, 

 varying from two to eight inches in thickness, and measuring in depth 

 two or three feet. They are crowded witli fossils having no place in the 

 Hamilton. The surface is roughened with the broken valves of a shell, 

 in external form closely resembling a Eenssellceria. In one portion of 

 each quarry these take the form of casts, and a continuous reef is pre- 

 sented to the eye, the greater number partially weathered, but so 

 imbedded in the matrix that while they exist by the thousand to the 

 thickness of a foot or more, and almost to the exclusion of any other 

 form, yet it is difficult to extricate a single individual from the mass 

 without breaking it, and its condition, then, is beyond the possibillity of 

 identification. These beds are wanting in the locality between Rock Island 

 and Moline. Underneath them we find the same fine grained grey or dove 

 colored limestones which are exposed in these quarries, and, I may add, 

 with their characteristic fossils. The series then, as a whole, is only 

 found on the Iowa side of the river. 



Above these beds and to the south of the quarries— in immediate con- 

 tact with them — we have as its uppermost limit the limestone of the 

 Hamilton. Its lower limits are equally marked, not only by a zone 

 below which fossils rarely appear, but there is a decided change in litho- 

 logical character. To the close grained compact limestone suc- 

 ceeds a rough rock, concretionary in appearance, closely approaching the 

 character of chert. In Cook's quarry (and I suppose the same 

 would hold true in reference to Smith's), the workmen only blast 

 down till they come to what they call " the flint rock." Mr. Cook told 



