Hi Linda @lmccall –Thanks!
The Miocene land mammals should be coming from the lower (older) units and would include land mammal teeth and bones (not marine species) that would occur mixed along with marine critters. I am excited to know that your club might have some good stuff, because I was previously only aware of the handful of fossils in the Smithsonian (from Dave Bohaska @dbohaska). If your group has fossils, I’d love to see photos and then I can let you know if they are what we are looking for, or not.
All the best, Bruce