Thanks to all who have written on this topic. I am interested more in the methods of rediscovery than in specific cases, because they illustrate how anyone can rediscover a lost species (or discover a new one)--but it's always intriguing to hear the actual firsthand story! Judging from responses, species cannot be effectively rediscovered without accurate identification. Someone actually has to recognize the specimen, either by previous study or by realizing that it doesn't match any of the usual species for the area. There are two lessons here: "Know your species" and "Don't give up easily on identifications." Of course, freaks and juveniles are not included in most identification manuals, and they may look like new species until you're used to them. Get some help with those last few shells that you can't identify--I mean the last few shells that are in good shape, of course. Species are quite often discovered or rediscovered in routine surveys of river systems or other areas. There, the people conducting the survey are generally knowledgeable about the local fauna, and have a "search image" for supposedly extinct species. It is also common for species to be "lost" because the original description did not include a precise locality, e.g., "Amazon River" covers a lot of territory. Collectors, like detectives, have sometimes been able to track down the locality of a shell from all sorts of clues. For instance, "This looks like a species that hugs the rocks, so it would be best to look for it in the rapids." I don't know if anyone has ever used this particular clue, but the sediment remaining inside a shell can be very informative as to its origin. It may include rock grains or microscopic skeletons of algae or foraminifera of known range. So rediscovery can be deliberate as well as accidental. It may seem trivial to emphasize the importance of accurate identification, but consider this scenario. Suppose a collector identifies most of his or her shells from the Siwash River, but can't identify them all. Eventually they end up in a museum, and years later, Tom Watters or Kurt Auffenberg visits the museum and says, "Shazam!* Quadrula pastafazula was still living in the Siwash River only two decades ago! I'm packing my bags and waders to see if it's still there!" Wouldn't it have been nicer if the collector could have known? And it certainly would have been easier for Tom or Kurt to have a guide to the collecting site. And, of course, especially nice if the collector knew it for him- or herself, at the moment of collection. Watch out about collecting endangered species, though. A camera might be the way to do it, plus good field notes. Andrew K. Rindsberg (who rediscovered a species of Eocene chiton a couple of years ago in a routine survey) Geological Survey of Alabama *He probably wouldn't have said "shazam".