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