BONES AND GRAVEL: Members of a geology class at Eastern Michigan University in Ypsilanti check a human skeleton found yesterday at the top of a pit in Killins Gravel Co. at 3305 W. Liberty Rd. in Scio township. Two EMU students, Kay Volkmar and Elaine Pero, found a skull and minutes later discovered the bones while on a field trip with Prof. Norbert W. O'Hara's class. Sheriff's deputies turned the bones over to medical experts at the University of Michigan who said a preliminary examination indicated the remains are those of an American Indian buried several hundred years ago.