Abstract: The glochidia of Diplodon (Diplodon) suavidicus (Lea, 1856), D. (D.) obsolescens F. Baker, 1914, Diplodon (Rhipidodonta) hylaeus (d'Orbigny, 1835), Prisodon obliquus Schumacher, 1817, Paxyodon syrmatophorus (Meuschen, 1781), Triplodon corrugatus (Lamarck, 1819, and Castalia ambigua Lamarck, 1819 were redescribed based on comparisons of external morphology and morphometric measurements of larval shells. The outline of the glochidial valves was classified into three types. The morphological comparison was based on light and scanning electron microscopy. Details of the shell, hooks and external sculpture allowed a redescription of the larvae, transferring D. suavidicus and D. obsolescens to the subgenus Diplodon and, within the Prisodontini, the genus Triplodon Spix, 1827 was separated from Prisodon Schumacher, 1817 and Paxyodon Schumacher, 1817. The glochidium of Prisodon obliquus is described for the first time. The larvae of the latter species and those of Paxyodon syrmatophorus present projecti...