BRACHTOPODA OF THE RICHMOND GROUP 699 



The following two papers were read by title : 



THE AFTONIAN SANDS AND GRAVELS IN WESTERN IOWA 



BY BOHUMIL SHIMEK 



AN AFTONIAN MAMMALIAN FAUNA 



BY SAMUEL CALVIN 



Then was presented orally 



BRACHIOPODA OF THE RICHMOND GROUP 

 BY AUGUST F. FOERSTE 



[Abstract] 



In the area dominated by the Cincinnati geanticline there have been several 

 invasions of the brachiopoda considered most typical of the Richmond group. 

 The first of these occurred near the middle of the deposition of the Arnheim 

 bed. The Richmond group of the Mississippi valley, as far as may be deter- 

 mined from a study of the brachiopoda. finds nearer representatives in the 

 upper or Blanchester division of the Waynesville bed and in the Liberty bed 

 than in the Arnheim, Lower Waynesville, or Whitewater beds. A study of the 

 distribution of the brachiopoda in Ohio, Indiana, and Kentucky suggests that 

 the centers of distribution lay more frequently toward the northeast than 

 toward the northwest or west of the present areas of exposure. To account for 

 this, it is imagined that the Richmond group of the Ohio valley was connected 

 with that of the Mississippi valley by way of northern Indiana and Illinois. 

 Possibly, if the areas now covered by overlying formations could be exposed, 

 the Richmond brachiopoda would be found to be absent in southern Indiana 

 and Illinois and in western Kentucky, west of the present areas of exposure of 

 these fossils in the region of the Cincinnati geanticline. Lithological conditions 

 within the areas dominated by this geanticline favor this view. 



E. E. Cumings discussed this paper. 

 After this the following paper was read : 



TRAP SHEETS OF THE LAKE NIPIGON BASIN 

 BY ALFRED W. G. WILSON 



This paper has been published as pages 197-222 of this volume. 

 This paper was discussed by A. W. Grabau, A. W. G. Wilson, A. C. 

 Lane, and A. F. Foerste. 



