We thank P. M. Sadler and D. J. Strauss for helpful comments during development of this extension of their pioneering work on confidence intervals for stratigraphic ranges. Our results were first presented at the invitation of L. G. Barnes at the 1996 North American Paleontological Convention in Washington, D.C., and the paper was completed with support from National Science Foundation grant EAR-9714923. We thank N. MacLeod and two anonymous reviewers for reading and improving the manuscript.