It was with a great deal of surprise that I found mammal bones in the ero ding side of Sleeping Bear Dune in July, 1933. Bones usually decay quickly in sand deposits. Although these bones had been buried for perhaps a thousand years they seemed to be preserved unusually well. The geological history of Sleeping Bear Dune dates back to the late Wisconsin Glacial period. The dune is situated on the east coast of Lake Michigan about thirty miles northwest of Traverse City, Mich. It is perched on top of a high plateau laid down by glaciers. The plateau is 400 feet above Lake Michigan and the top of the dune was once 125 feet above the plateau (figure). According to early white explorers the dune was still at this height through the nineteenth century. The dune was wholly forested when first seen by white man and probably had been for several hundred years. Due to trails made by recent white man the wind on the lake side was given a chance to gradually erode the dune and undermine the vegetation, thus exposing the crest to disintegration. The lake side of the dune and the crest, becoming exposed, rapidly blew away. For the last few years this has been taking place at the rate of about three feet a year, until now the top is only about ninety feet above the plateau. The inland side still remains densely covered with vegetation.