Sylvia and other Conchlers, The number of molluscan species is only significant when the number is put to use somehow, so I think it's fair of me to ask, "Why did you want to know?" Here are some reasons why I'd like to know. First off, obviously, we all want to know how many species there would be in an imaginary Museum of All the Mollusca. It would be well worth knowing how complete are the world's greatest collections, who collected the most species in a lifetime, and how they did it. I'd like to know how many of those species live in each major type (biome) of biological environment (deepsea, coastal, freshwater, land, etc.). Which one has the greatest diversity of mollusks overall? Which one has the greatest diversity of mollusks per area? (The deepsea environment is the largest one on the planet; the freshwater biome is comparatively small.) How diverse are the mollusks compared to other major groups (phyla) of animals, such as echinoderms, arthropods, and chordates? What has made the mollusks so successful compared to other animals? Does their success depend on particular features of their biochemistry? behavior? anatomy? Was their success inevitable in Earth history, or was it a matter of luck (being there at the right time and place)? Have the mollusks always been this diverse, or has their number of species increased or decreased through time? Why? Are the mollusks equally diverse in every climatic zone? Of course not, but where is the diversity the highest, and how did that happen? Which kinds of mollusks are the most diverse: those that burrow in the sand or mud, those that bore into rock, or those that lie on the surface of the seafloor? Which classes and families within the Mollusca are most diverse? On the whole, are the rare species more diverse, or the common ones? Given two molluscan provinces on either side of a continent such as North or South America, do these provinces have the same diversity? In the Permian Period, there was only one large continent, Pangaea. Today the continental land masses are broken up and dispersed around the globe. Does the arrangement and number of continents make a difference in molluscan diversity, even if the land area is the same? How many of the world's mollusk species are recently extinct or threatened with extinction? And are these mollusks concentrated in any particular region, biome, or climatic zone? And again, why? Well, Conchlers, you have now gone through a list of questions that might be presented to a doctoral candidate in malacology at his or her oral and written examinations. The books of Peter Dance, Geerat Vermeij, and James Valentine answer most of them. Of the Conchlers, Gary Rosenberg has spent a great deal of his career answering some of these questions. I don't intend to answer the questions on-line, since these other people have already done a great job in print, but I just want to suggest some of the reasons why the question, "How many species of mollusks are there?" is a lot deeper than it sounds at first. It really is worth an answer. Now, how does someone go about counting all the mollusk species that have ever been named? It would help if someone had prepared a checklist. As it turns out, the Zoological Record has attempted to do exactly that on a yearly basis for ... hmm... if memory serves, about 150 years. Only about half of the way back to Linnaeus, but a far way nonetheless, and probably including most species that have ever been named. No one has yet compiled their annual lists into a single long list, as far as I know, but the ZR is being placed on-line and it will not be many more years before such a list can be compiled electronically, and very quickly. Check out their Web site. Such lists have been compiled for various regions, however. These lists could be collated to make a "master list" of Mollusca. Tucker Abbott, in "American Seashells" (1974), recognized 6500 species from the seas off North America. Gary Rosenberg has posted a regional list for the Western Atlantic on the Web. It may be too big for some people to access (I know my old computer couldn't do it). Does anyone care to announce the number here? Abbott also compiled a master list of Land Snails, but I don't have that book here at the office. (Anyone have it handy?) The Treatise on Invertebrate Paleontology is of some help, because this series attempts to describe every genus of fossil invertebrate. Genera, not species, but that's something. So far, there are six volumes on Mollusca, some of them 30 years out of date, but only one volume has been published yet on the Gastropoda. That's a lot of fossils. Warren Allmon, who heads the Paleontological Research Institution in Ithaca, New York, is also the head of a massive, long-term project to complete the part on Gastropoda. Anyway, one could simply count the valid genera in the indices; the invalid ones are conveniently italicized and the valid ones are not. Sepkoski has compiled the numbers of genera per family for each invertebrate group through time from the Treatise. This compilation is flawed because the Treatise is flawed, but the data exist. (Sorry, the University of Alabama didn't buy that book; I've never seen it!) Finally, some museum collections have been cataloged in such a way that the number of species can be obtained without difficulty. (Kurt, if you're lurking out there, this is your chance to show us how it's done!) At least in principle, it will not be many tens of years before most museums have such catalogs, and this is another potential source of information on numbers of species form particular regions. The best such lists are those that are compiled by a single person, or a small team, from the specimens themselves, not from lists in books, not just because so many (half?) of the species names are synonyms (tip of the hat to Helmut), but because a great many museum specimens have old and inaccurate labels (thanks, Kurt). So it will take a lot of work to compile even a rough checklist of the world's molluscan species. But we will probably have that within a few years, as the Zoological Record digitizes its back issues. Have a great weekend, shell maniacs! Andrew K. Rindsberg Geological Survey of Alabama Tuscaloosa, Alabama, USA