This is a yet-unnamed Powelliphanta species, provisionally known as Powelliphanta "Matiri". This is one of the amber snails. It is an undescribed species of large, carnivorous land snail, a terrestrial pulmonate gastropod mollusc in the family Rhytididae.
References
Powell A W B, New Zealand Mollusca, William Collins Publishers Ltd, Auckland, New Zealand 1979 New Zealand Department of Conservation Threatened Species Classification Department of Conservation Recovery Plans