Nora, I thought your question was quite a good one, but meant to say that nature doesn't always cooperate with our own, very human categories and ideas. In particular, language does not always match reality very well, so we can ask a precise, crisply worded question and be appalled by the vagueness of the answer, yet learn something from the discussion. A favorite example of this kind of problem is to point out that we have words for "blue" and "green", but no two people agree on exactly where blue stops and green begins. This doesn't mean that blue and green are meaningless concepts, however; most of the time we have no difficulty in distinguishing them. Another perennial question of this nature includes, "What is a species?" Yes, the word "species" is applied differently for fossils than for modern organisms, because the fossils are incomplete and generally lack soft parts, DNA, pigment, etc. (Think of all those cones and cowries that are distinguished largely on the basis of color!) The word "species" is still meaningful for fossils, because it is applied consistently; species of fossil mollusks are based on the shape, internal structure, and composition of the shell. We only get into trouble when we slip and try to use modern and fossil species in the same database interchangeably, without making allowances for the differences. And actually, the differences between fossil species and modern species are not as great for the Mollusca as they are for some other groups of animals, so we're not in as bad a shape as all that. We paleontologists endeavor to persevere. Andrew K. Rindsberg Geological Survey of Alabama