Nancy Smith asks how you can distinguish modern and fossil shells. The first thing to realize is that time is continuous, so all stages exist between a mollusk at the moment of death and a shell that has been dead for millions of years. There are plenty of meaningful events that can change a shell, but not all of them are as sudden as death or burial. Some of them can be very slow, like recrystallization. We had a big discussion about what "fossil" meant a few months ago and I have no intention of encouraging that to start up again. It does not have a definite answer. What most people mean by "fossils", most of the time, are remains that are OLD (generally older than 10,000 years), somewhat ALTERED from their original state, and BURIED (the word "fossil" means "dug up"). Often they are the remains of extinct animals, but this is not necessary. Old? Radiocarbon testing can determine if a shell is about 50,000 years old or less, since shells are made of calcium carbonate and contain quite a lot of carbon. After about 50,000 years, the radiocarbon has decayed to the point where not enough is left to measure accurately. I take it that you do not have a mass spectrometer and about a hundred dollars per sample? And you want the sample to be intact afterward? <sigh> Well, I don't have one either. Other methods exist (amino acid racemization, for example), but not available without a lot of technical equipment and knowledge. Altered? You can look at a shell and see whether it has been "aged" by dissolution, abrasion, drillholes, borings, breakage, cementation, recrystallization, alteration to other minerals, etc. But some of these processes are quick and can happen even in living shells. A shell washed out of a Miocene deposit can sometimes be fresh enough to be mistaken for a modern shell. If it belongs to a species that has changed little for millions of years, it may be very difficult to determine that you have a fossil. Let's return to that general concept of "fossil": Old. Altered. BURIED. Context is important in archaeology; it is just as important in paleontology. A seashell buried in loose sand on the beach is not likely to be a fossil. A shell found in road metal a hundred miles inland is likely to have been transported; it is out of context. But a seashell buried in firm sand a hundred miles inland is, particularly if it is extinct and so are a lot of the other species along with it. Context is important. Clear as mud? So is the concept of "fossil"! Andrew K. Rindsberg Geological Survey of Alabama