Drepanostoma helenae, a new helicodontine land snail from the Lower Pliocene of Balze di Caspreno near Siena (central Italy) and a discussion on the status of Protodrepanostoma Germain, 1929 (Gastropoda, Pulmonata: Hygromiidae). Bollettino della Societa Paleontologica Italiana, 39(3) 2000: 351-358. 351 [Zoological Record Volume 137]