Bathytoma mitchelsoni
Bathytoma mitchelsoni is an extinct species of sea snail, a marine gastropod mollusc in the family Borsoniidae. A species that lived on the bathyal sea floor, fossils of the species date to the early Miocene strata of the west coast of the Auckland Region, New Zealand.
Description
In the original description, Powell described the species as follows:
The holotype of the species measures in length and has a diameter of. It can be differentiated from other New Zealand members of Bathytoma due to having finely gemmulate periphery and basal spirals, and from B. haasti due to B. mitchelsoni having a significantly lower keel that almost touches the lower suture, and due to its finer and more numerous gemmules.
Taxonomy
The species was first described by A. W. B. Powell in 1935, naming the species after politician Edwin Mitchelson, on whose property the holotype was discovered. The holotype was collected at an unknown date prior to 1935 from between Powell Bay and Bartrum Bay, south of Muriwai, Auckland Region, and is held in the collections of Auckland War Memorial Museum.
This extinct marine species occurs in early Miocene strata of the Nihotupu Formation of New Zealand, on the west coast of the Waitākere Ranges of the Auckland Region, New Zealand. The species lived in a bathyal habitat. The Powell Bay site deposits of the Nihotupu Formation in the western Waitākere Ranges are mid-bathyal, while the Shaw Road quarry in the eastern Waitākere Ranges where B. mitchelsoni has also been found is an area of sea-floor deposits from the bathyal and abyssal zones, which likely had temperatures that fluctuated between 4-10°C.