1. Department of Earth Sciences, 1272 University of Oregon, 100 Cascade Hall, Eugene, Oregon 97403-1272, U.S.A.
2. University of Oregon Museum of Natural and Cultural History, 1680 East 15th Avenue, Eugene, Oregon 97403, U.S.A.
3. Linfield College, 900 SE Baker Street, McMinnville, Oregon 97128, U.S.A.,
4. Current address: Department of Geology, Occidental College, 1600 Campus Road, Los Angeles, California 90041, U.S.A.
5. Robert D. Clark Honors College, 1293 University of Oregon, Eugene, Oregon 97403-1293, U.S.A.,