Wow, you've collected some nice fossils! There's a friend of mine here in town (Memphis, TN) who sells Hell Creek microfossils collected from ant hills in South Dakota. The ants excavate the fossils, along with dirt, as they build their nests. These fossils are out of their original position and therefore are not extremely useful to academic paleontologists. My friend is very knowledgable on the subject and has quite a collection of identified microfossils. Here's a website for a few of the mammal teeth:
http://www.ddfossils.com/cretmam.htmlI hope this helps you out a little.