07/11 Quick guide to common New Zealand freshwater Mollusca Prepared by Brian Smith (2007) Sphaeriidae YES Is the shell <6 mm & pale? Bivalvia NO (clams) Cucumerunio YES Hyriidae Does the shell have distinct nodules & ridges? note: juvenile Echyridella NO have distinct ridges present Echyridella YES Is the shell composed of 2 halves & cockle- like? generally restricted to Melanoides thermally (exotic) influenced waters YES NO Is the shell strongly elongated (tips may Gastropoda be broken) & (snails & distinctive striae limpets) present? shell dark & smoothly coiled, up to 30 mm Prosobranchia YES NO Melanopsis Is an operculum Melanopsidae present, & the shell always spired? YES NO Is the shell smoothly coiled, with a large white mantle on the ventral surface? NO usually <12 mm, may have spines Hydrobiidae Potamopyrgus Continued overleaf Continued from previous page shell up to 12 Latia mm Latiidae Pulmonata YES Is the shell black, & oval to rounded, dorsally? YES NO pale, shell sub- Ancylidae parallel sided, Ferrissia Does the shell lack a YES Is the shell dorsally; <5 mm distinct spire, or domed & does the specimen limpet-like? look limpet-like? NO Gyraulus NO Planorbidae (in part) YES shell spire of Is the shell <5 mm dia, & variable height shell flattened like a coin? Planorbella (exotic) YES NO Is the shell very thin & brittle, & the blunt end smooth with fine grooves? NO shell up to 30 mm Planorbarius dia; (exotic) digitate process Physa Physidae (exotic) YES Does the YES shell open on Is a digitate process present on inner mantle opening; the left hand side? shell never with carina? NO NO Planorbidae Lymnaeidae (in part) shell spire rounded Glyptophysa to carinate Lymnaea (exotic) striations at right angles to growth lines YES Pseudosuccinea (exotic) Is the spire acute & elongate? YES Are there striations at NO right angles to growth lines, & the body shape not noticeably bulbous? NO Austropeplea image courtesy of S. Moore, Landcare This Quick guide was funded by Terrestrial and Freshwater Biodiversity Information System (TFBIS) programme number 194 . .