I made contact with Larry Kinsella and he informed me that some of the shells are marine and some are freshwater. The really thick ones were freshwater. He suspects a species known as a Three ridge was the source. I tend to agree. Three ridge mussels have thicker margin and are fairly tough. They were excavated from a number of Woodland and Mississippian archeological sites with holes drilled in them for use as hoes. I suspect they were also used for scrapers and other tool/art craft. My ultimate goal is to replicate one of these atlatls.
Apparently I can purchase asphaltum in the hardware store. Henry's Asphalt Emulsion, comes in a blue and white can and has been reported to me as essentially the same stuff. Kinsella posted that he has used asphaltum to affix his bannerstones and the stuff is nearly impossible to disassemble once set. I recall some discussion on the PA site about bannerstones sliding. I thought that was not possible before but now I am double against that notion.
I always thought there were two primitive adhesives, pitch and hide glue. Not so. I have more to learn
I think Native people thought about shells the way we modern bowers think about wood. Each species has it attributes and uses. We are not connected to that knowledge today.
DK, That is an interesting observation about pocket mussel effigy pottery. I have seen effigy pots of whelks and conchs, but never freshwater mussels. Do you have any images of that?