Figure 1. View of that portion of the Cedar Valley limestone im- 
mediately below the Acerz'ularia daz-idsoni Coral reef, which is the over- 
hanging ledge at the top of this exposure along ]klill Creek. Rock Island 
count%'. Illinois. The characteristic oblique jointing of some of the beds is 
quite distinct.  
Figure 2. View of an outcrop of the lower portion of the Cedar  
Valley limestone along Mill Creek. Rock Island count>-. Illinois : the  
lowest block in the right-hand corner is the top of the Phillipsastrea ozne.  
which marks the uppermost layer of the Wapsipinicon stage. 
