Manitoulin Fossil (#8)

Does anyone know what this is? The marine fossils on Manitoulin Island, Ontario, are associated with two geological periods—the Upper (Late) Ordovician (approx. 460.9 – 443.7 million years ago) and the Lower (Early) and Middle Silurian (443.7 to 422.9 million years ago). At this time, the island was near the equator and covered with shallow tropical seas. The fossils I’ve found tend to be either Bryozoan colonies or Favosites (Tabulate Corals— polygonal “honeycomb corals” or polygonal “wagon wheel” corals). But this one doesn't appear to be anything like those. The long plant-like object is 3 1/4 inches long (85 mm). I've shot it on a slight angle to emphasize the shadows--the 3D look it has. The triangular object at bottom looks like a tooth; I wonder if it's a bivalve.