Napean Island Amber Snail (Spirancinea napeanensis)
This species was described in 1913 based on subfossil shells that were found on the tiny Napean Island offshore the southern coast of Norfolk Island. The shells show a wide variability and thus were originally described as two species, which subsequently were synonymized with each other.
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The Napean Island form could well be conspecific with the Norfolk Island Amber Snail (Spirancinea norfolkensis (Sykes)) or could be assigned to that species as a subspecies.
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References:
[1] Tom Iredale: The Land Mollusca of Norfolk Island. The Australian Zoologist 11: 46-71. 1945-1951
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edited: 29.03.2021