18 PROCEEDINGS OF THE NATIONAL MUSEUM vol.70 



streams around Oregonia, Ohio, it is fairly common within the 

 narrow limits of its range. Although detached brachial and pedicle 

 valves are equally common, we have never collected a specimen with 

 these valves found in their natural position. 



Ptilodictya nodosa (James) : The type of this species was collected 

 by the late Dr. L. B. Welch from a limestone layer at the mouth of 

 Cowan Creek, Clinton County, Ohio. The strata at this point be- 

 longs to the Blanchester division and comes in at about the level 

 of the coral bed (W. 15). This apparently marks its pomt of en- 

 trance into the Richmond of this region. Its range extends upward 

 through the remainder of the Blanchester through the entire thick- 

 ness of the Liberty and up 15 to 20 feet in the Whitewater. This 

 is a rare form throughout its entire range. 



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