Named after my niece Gemma Lim. This subspecies is found 100km apart from the nominal species and has a smooth shell. The originally described subspecies has a very rough and rugged shell. The shape is also round and regular for the gemmalimae while the nominate species has an irregularly shaped shell. Another big difference is the gemmalimae is a fully dextral species while the costifer costifer comes in both sinistral and dextral forms.