While not all of these specimens are truly microscopic, most require magnification to adequately see them. These are specimens picked out of gravel from the Three Lakes Creek on the NW side of Gainesville, Florida. Most specimens originate from the Miocene aged Hawthorn Formation. Thanks to @digit for providing the collecting opportunity as well as innumerable aids in the identification.
Four main sources (in no particular order) were used to identify the fossils:
1: FPS Special Paper by Boyd (2016) called "Fossil Sharks and Rays of Gainesville Creeks Alachua County, Florida"
4: "The Fossil Vertebrates of Florida" edited by R.C. Hubert, Jr.
I have done my best to get an accurate ID, but certainly if you see one in need of a correction, please let me know. Thanks