What's interesting with these lists of families with sole surviving members is that so many of them were present in Cretaceous rocks, more than 60 million years old. They have survived a long, long time. Some of them were not very prolific then either, like the Pulvinitidae. But there were lots of species of Trigoniidae. What is their future, I wonder? Will they dwindle to nothing? Or will they blossom from a single species into many, like the sea urchins did after the mass extinction at the end of the Paleozoic? Andrew K. Rindsberg Geological Survey of Alabama