Discus-shaped Bermuda Land Snail (Poecilozonites nelsoni ssp. discoides)
The Discus-shaped Bermuda Land Snail was described in 1904 as some kind of form of the the Bermuda Land Snail (Poecilozonites nelsoni (Bland)), it might have been a distinct subspecies or perhaps nothing but a distinct-shaped form. [1]
This snail is now apparently extinct.
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References:
[1] Addison Gulick: The fossil land shells of Bermuda. Proceedings of the Academy of Natural Sciences of Philadelphia 56(2): 406-425. 1904
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edited: 11.09.2020