20 DAVENPORT ACADEMY OF NATURAL SCIENCES. 



Fossils assume a greater variety of forms. There is an increase both 

 in the number of species, as well as multiplicity of individuals. 



Adopting the same order as before, we may revisit the LeClaire 

 quarry. Though limited in extent, the lithological and faunal differ- 

 ences are at once recognized. The soft clay enclosed a profusion of 

 small fossils. With the minute, frail, delicate bryozoa were mingled 

 brachiopods equally small and delicate. The limestone carried the 

 common forms. Of the two American species of Hexacrinus, one was 

 found in the encrinal limestone of this quarry. The Academy was 

 fortunate in having it studied, described and figured by Messrs. Wachs- 

 muth and Springer, who gave it the name of Hexacrinus occidentalis. * 



Of these beds, as exposed in Rock Island, no later or better summary 

 can be given than that by Prof. Udden.f The section described was 

 near the Rock Island depot, and divided into three parts : " The upper 

 twenty feet was composed of shaly limestone and calcareous shale, con- 

 taining throughout fossil brachiopods and, near the top, stems of vari- 

 ous crinoids. The next six feet comprised three ledges of limestone 

 separated by seams of shale, and containing about the same fossils as 

 the beds above. The lower consisted of three solid ledges of a strong 

 limestone, seven feet thick, containing a less number of brachiopods 

 and more corals." The two upper portions represent the Spirifer 

 Pennatus beds, the lower, the Phragmoceras. 



From this bluff exposure at Rock Island, crossing the river, we de- 

 scend to the low bottom land below the city in which Cook's and 

 neighboring quarries were wrought. The entire mass of the Spirifer 

 Pennatus beds has almost disappeared. The bluff from which they 

 were detached is more than a mile to the northward. The surface 

 rock through that whole distance is the Newberria strata of the Phrag- 

 moceras beds, and only in its slight irregularities and shallow troughs 

 are traces of the shale to be found. At the quarries the limestones and 

 shales represented at Rock Island by over thirty feet of thickness have 

 dwindled down to two or three feet, still carrying their larger fossils. 

 Underneath is a soft clay like that in the LeClaire quarry, crowded 

 with exquisitely-preserved small brachiopods and as equally delicate 

 small bryozoans. There is no further exposure through a distance of 

 five or six miles, where we reach the quarry of Mr. John Sauer. It is 



*Nortli American Crinoidea, by Wachsmuth and Springer, Vol. II., page 745, and Atlas, 

 Plate Ix.xviii., tig. 10. 



t Report of the Illinois Board of World's Fair Commissioners at the World's Columbian 

 Exposition, page 136. 



