The Smithsonian has a collection for a geologist named Henry Nettelroth (1835-1887) and they have some reports I found on-line. I think they are from the mid to late 1800s when a lot of the fossils in the Louisville area were named. Nettelroth refers to the Silver Creek formation as "hydraulic limestone". Also he refers to Clark County as Clarke County. I have also seen Speed, Indiana USA referred to as Speeds, Indiana in older texts.
UPDATE: This entry has been modified with a picture of another clam fossil. As of August 2010, this fossil was on display at the Smithsonian Museum of Natural History. It list it was found in Kentucky.
