258 REVIEWS 



more closely related to the St. Louis group than to the Chester with 

 which Ulrich had allied it, chiefly due to the presence of a species of the 

 typical Chester genus Coeloconus. On this basis and the recent recogni- 

 tion of an unconformity separating the Renault and Ste. Genevieve 

 formations, Weller redefines the Meramec group so as to include the 

 Ste. Genevieve. 



This report represents the most recent work on the subdivision of 

 the Chester and the correlation of these units. Especial attention is 

 called to the following corrections of previous correlations of the forma- 

 tions of southeastern Illinois and Kentucky with those of Randolph 

 County: (i) the Renault and Shelterville formations, the Upper Ohara 

 of Ulrich, are correlated with the Renault. Professor Weller considers 

 those species of the genus Talarocrinus with the thickened plates form- 

 ing bilobed basis as very characteristic of the Lower Chester. This 

 fauna is typically developed in the Upper Ohara; (2) the Golconda 

 limestone with the Lower Okaw; (3) the Cypress sandstone with the 

 Ruma; and (4) the Bethel sandstone with the Yankeetown formation. 

 Methods of correlation are discussed in detail. 



The igneous rocks of the region are found chiefly in the vicinity of the 

 Ohio River where the more rapid erosion has exposed them. They are 

 of three types: fine-grained, dark-colored lamprophyres, medium- 

 grained, dark-colored peridotites, and volcanic breccia. 



Economically Hardin County is noted for its fluorite deposits, the 

 annual output of the county being over two- thirds that of the country. 

 Fluorite occurs as (i) vein deposits, replacing calcite fillings of the 

 fault planes; (2) bedded deposits where fluorite has replaced limestone 

 bedrock; and (3) superficial residual deposits. Small quantities of 

 lead and zinc are recovered incidental to the fluorspar exploitation. 

 The origin of the deposits involves (i) doming and faulting in post- 

 Pennsylvanian, (2) deposition of calcite in the fault fissures, (3) minerali- 

 zation by Auriferous magmatic solutions replacing calcite, and (4) the 

 introduction of metallic sulphides. 



The only other large resource of the region is agriculture. There is 

 an abundance of limestone suitable for lime, cement, and ground rock 

 for fertilizer, as well as an unlimited supply for road metal. In regard 

 to the oil and gas possibiKties, while the structure is favorable, but Httle 

 is known of the underlying pre-Devonian sediments. 



In the portion of the bufletin devoted to systematic paleontology^ 

 the work is limited to those common species in need of further illustra- 

 tion and description and to those forms important for their bearing upon 



