Pisinna rekohuana

Holotype of the subspecies Pisinna rekohuana lactorubra

Powell described the species as follows:

Shell small, ovate, solid. Whorls 4¾, including low dome-shaped protoconch of 1¾ whorls, which is faintly sculptured with closely spaced spiral striae. The surface of the post-nuclear whorls is smooth, but not polished, and apart from faint, slightly oblique axial growth lines, there is no true sculpture. Spire elevated, bluntly conical, one and a-half times height of aperture. Colour reddish-brown, except for a narrow whitish band immediately below the suture, and the peristome and interior of the aperture, which is more yellowish than reddish-brown. Aperture very large, almost circular. Peristome continuous, much thickened within and clearly marked off from the base by a heavy callus. There is no umbilical chink.[2]

Pisinna rekohuana is similar in appearance to Pisinna minor and Pisinna subfusca, and can be identified by its size (intermediate between the two) and relatively larger aperture.[2]

A subspecies, Pisinna rekohuana lactorubra, was described in 1965 by Winston Ponder, differentiated by its proportionately longer spire and different colour pattern.[3] While Ponder noted a similarity of Pisinna rekohuana lactorubra to Pisinna zosterophila, he believed it was best to classify it as a subspecies of Pisinna rekohuana, due to its distribution and the relationships of forms between the three groups.[3]

The species measures 2.0mm, by 0.9mm,[4] while the subspecies Pisinna rekohuana lactorubra measures 3.2mm by 1.5mm.[5]

The species is endemic to New Zealand.[1] The holotype was collected by Powell himself in February 1933 at Waitangi, Chatham Islands.[6] It is found around the South Island,[7][8][9] in the waters of the Chatham Islands, commonly at Stewart Island, the Auckland Islands and the Kermadec Islands.[2][10][11][12]

Pisinna rekohuana lactorubra is primarily found to the north-east of North Island under stones in the littoral zone, preferring open coasts.[3] It has been identified on Manawatāwhi / Three Kings Islands,[13] the Manukau Harbour on the west coast of the North Island,[14][15] and the Mahia Peninsula.[16]

Since the subspecies was first described, Pisinna rekohuana rekohuana has been identified as living in the range previously thought to be that of Pisinna rekohuana lactorubra, such as the north-east coast of the North Island,[17][18][19] and the Mahia Peninsula.[20]