This form differs from the nominate form by its smaller size, its compact and closely coiled spire, but especially in its smoother surface marked with finer and more distantly spaced growth-wrinkles. [1]

“This is an exceedingly rare form of Amastra. the results of five findings are six whole and three broken specimens. Among the large number of Amastras that have been taken in the Manoa fossil deposits, from the beginning of Oahu Avenue to Awapuhi Street, this form was only taken from four “pockets”.” [1]

These deposits appear to be actually Late Pleistocene to early Holocene in age.

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References:

[1] C. Montague Cooke: New species of Amastridae. Bishop Museum Occasional Papers 10(6): 1-29. 1933

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edited: 04.05.2022