Revision of the genera of Scolodontidae, part 2: Guestieria Crosse, 1872, Xenodiscula Pilsbry, 1919, and a misidentified planorbid

Currently, there are many issues with genus-level taxa within the Scolodontidae. This is the second paper in a series which aims to resolve the most prominent issues. Here, we highlight some of the more poorly known, smaller, discoid genera: Guestieria Crosse, 1872 and Xenodiscula Pilsbry, 1919. Guestieria is characterized by its small to medium-sized shell (2–18 mm), without or with only faint sculpture, and with a covered apex and closed umbilicus. Its known geographic distribution is confined to Andean countries and Brazil. Xenodiscula is small (up to 1.6 mm), discoid, and with prominent apertural barriers not seen in other scolodontids. Its known geographic distribution included all of the Amazon rainforest, the Tumbes-Chocó-Magdalena hotspot, and mainland Central America. We also discuss the enigmatic Guestieria shuttleworthi (L. Pfeiffer, 1851), which we show is a junior synonym of the planorbid freshwater snail Drepanotrema anatinum (d’Orbigny, 1835).