Stylidium macrocarpum (Benth.) F.L.Erickson & J.H.Willis and S. leptophyllum DC. var. glabrescens Mildbr. are placed into synonymy under S. rigidulum Sond. and a revised taxonomic description provided. A modified description is also provided for the morphologically allied S. kalbarriense Lowrie & Kenneally. A chromosome number of n = 13 is reported for S. kalbarriense, and a count of n = 11 confirmed for S. rigidulum. These species are noted to grow in sympatry east of Dongara. Both taxa are susceptible to infection by the rust Puccinia stylidii McAlpine.