A large family, with a great diversity in shape. Not very popular among collectors, partly also because of their small size. Interesting are the large Fissurella from Southern America. A few of the minute members from the genus Emarginula are much sought after by European collectors. About 300 species.
For a list of genera and species:
http://www.marinespecies.org/aphia.php?p=taxdetails&id=111