From card: "According to the tag this was secured by a Crow medicine man for use in ceremonials [sic]. It is probably a ball of hair [bezoar] which is often found in the stomach of ruminent animals"
Timothy McCleary, from Little Big Horn College, pointed out that this is technically a bezoar, not a cud, as originally catalogued. It is a large, hard stone-like object that would have been removed from the stomach or intestines of the bison as it was butchered.