There are numerous literature records for Desoria olivacea (formerly Isotoma olivacea) but I have not seen a specimen of this species collected from UK/Eire. The mucro has four teeth and a lateral seta (see Potapov (2001) for a full description). None of the specimens labelled 'Isotoma olivacea' in the NHML slide collection have a mucro with a lateral seta and all key out to Desoria tigrina. The confusion has arisen because the descriptions of Isotoma olivacea in several earlier identification keys, including Gisin (1960), were in fact for Desoria tigrina. However, the true Desoria olivacea may turn up in the future.

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