A new species of Ammonicera (Omalogyridae, Allogastropoda) from Brazil

Ammonicera plana, a new species of Omalogyridae, is described from the infratidal zone of the north coast of São Paulo State, Brazil. Distinguishing shell characters are; five dark spiral bands per whorl; great lateral compression; poor development of shell sculpture and the presence of a lateral spiral ridge. The anatomy is compared with that of the European Omalogyra atomus, from which it differs; in having mixed testis and ovarium; no large glands near the anus and in lacking vesicula seminalis. The anatomical data support the inclusion of the Omalogyridae in the Allogastropoda rather than in the euthyneuran Rissoelloidea.