330 Foerste — Ordovician-Silurian Contact in the 



north the upper part of the Madison bed, 14 feet thick, is 

 again massive brownish and sandy ; the middle and lower part, 

 40 feet thick, is soft and weathers readily ; Colurrmaria 

 alveolata occurs at the base, and Tetradium, is found 8 feet 

 higher up. A mile and a half farther north, at Belleview, 

 that part of the section equivalent to the upper part of the 

 massive bed, 20 feet thick, is again more calcareous, of a more 

 whitish or bluish color, sometimes slightly tinged with 

 purple ; it has a much more calcareous appearance, often 

 weathers very irregularly, and evidently corresponds' closely in 

 appearance to the greater part of the Madison bed as exposed 

 at Versailles, New Marion, Butlerville, Nebraska, and north- 

 ward as far as Osgood and Zenas. This whitish or bluish 

 calcareous form of the Madison bed is the phase most character- 

 istic of the area in which the Clinton is absent, and in the areas 

 immediately adjacent. In this whitish or bluish, more calcar- 

 eous phase of the Madison bed, fossils, especially bryozoans, 

 are less rare, and at some horizons, especially near the top, are 

 even common locally. That part of the Madison section at 

 Belleview which corresponds to the lower part of the massive 

 division of the section at Madison, retains its brownish, more 

 massive appearance and its practically unfossiliferous character. 

 This part of the section, 15 feet thick, may be traced north- 

 ward to Versailles, where it forms the unfossiliferous brownish 

 shales, 9 feet thick, immediately overlying the Tetradium bed. 

 These unfossiliferous shales occupy the same position along 

 the stream following the old right of way formerly used by the 

 Baltimore and Ohio Southwestern railroad 2 miles northeast of 

 Osgood. 



The fauna occurring at the top of the Madison bed at Madi- 

 son, Indiana, including Zophospira hammelli, Holopea hub- 

 bardi, and other fossils, may be traced northward 2 miles 

 beyond the line between Jefferson and Ripley counties. This 

 fauna is not confined to the top of the Madison bed, but may 

 occur at several levels, although always in the upper part of the 

 Madison bed. Occasionally it occurs in the upper part of the 

 layers which are equivalent to the more massive part of the 

 Madison section, sometimes even 7 feet below their- usual hori- 

 zon. Farther northward, in Ripley county, in the adjacent 

 part of Jennings county, and in the greater part of the area from 

 which the Clinton is absent and within which pebbles are 

 found in the Clinton, the equivalents of the Lophospira ham- 

 melli and Holopea hubbardi beds consists of sandy clays and 

 clayey limestones containing numerous branching bryozoans 

 and also a fair brachiopod fauna. These beds are described 

 in the following paragraphs. 



A mile and a half south of Versailles, south of the home of 

 William Rosengarn, the sandy clay at the top of the Madison 



