The ultimate goal of this project, The Conchological Albums - Terrestrial Molluscs, is to figure the world's biodiversity of land snails as completely as possible. Volume 20 of this series figures 606 shells of the Gastrodontidae and Geomitridae that belong to 304 different species and 39 subspecies.
Treated genera: Aegopinella, Gastrodonta, Glyphyalinia, Janulus, Mesomphix, Nesovitrea, Perpolita, Poecilozonites, Retinella, Striatura, Ventridens, Vermetum, Zonitoides, Actinella, Callina, Caseolus, Cochlicella, Discula, Disculella, Domunculifex, Geomitra, Helicomella, Hystricella, Monilearia, Obelus, Ponentina, Pseudocampylaea, Serratorotula, Spirorbula, Wollastonaria, Zarateana, Alteniella, Backeljaia, Candidula, Cernuella, Helicella, Helicopsis, Microxeromagna, Orexana, Plentuisa, Pseudoxerophila, Trochoidea, Xerocrassa, Xerogyra, Xerolenta, Xeroleuca, Xeroplana, Xerolexa, and Xerotricha.