Rissoa parva on left and centre, , H. 2.5 mm and 3.1mm . 1: purple/black peripheral line on foot confined to proximity of transverse band on side of foot. 3: Whole of opercular lobe is dark pigmented. 5: Opaque whitish posterior pedal gland extends almost to edge of narrow foot.
P. inconspicua on right, H. 2.6 mm. 2: purple/black peripheral line on foot extends well beyond transverse band on side of foot; often indistinct. 4: only anterior of opercular lobe is dark pigmented, posterior is pale. 6: Opaque whitish posterior pedal gland stops well-short of edge of wider foot.