THE STRATIGRAPHIC CONTEXT OF THE LATE CAMBRIAN TRILOBITE WALCOTTASPIS VANHORNEI FROM THE UPPER MISSISSIPPI VALLEY, AND ITS MORPHOLOGICAL VARIATION
SRIVASTAVA, Shravya, Department of Earth and Planetary Sciences, University of California Riverside, Riverside, CA 92521 and HUGHES, Nigel, Department of Earth and Planetary Sciences, University of California, Riverside, CA 92521