Pholadomya maoria n. sp. Shell very similar to P. pacifica Dall from the north-west Pacific and Japan, whitish, very thin, the beaks rather behind the anterior third. Inner layer pearly. Anterior margin evenly rounded, posterior end considerably more attenuate and with a considerable gape, posterior extremity evenly rounded. Hinge line thin, details of chondrophore and nymph much as described and figured for pacifica. Right valve apparently rather overlapping the left along the postero-dorsal margin in life. The thin shell and highly polished interior obscures the details of muscle scars and sinus, but the details appear very similar to those developed in pacifica. Interior strongly grooved by the major radial folds. Exterior dull, sculptured with strong radial folds over the central part of the shell, radials becoming obsolete anteriorly and posteriorly. There are eight major radials with finer intermediate radials. Rest of shell sculptured with very fine hair-like radials. Radial sculpture crossed by irregular growth folds and microscopically fine growth lines. Whole surface finely granulose except around the beaks where fine surface sculpture has been eroded. Length, 28mm; height, 19mm; distance from beaks to anterior end, 17mm. Holotype (M. 16253) and paratypes (M. 16257) in Dominion Museum. LOCALITY: Haul 5-Between Aldermen and Red Mercury Islands, 340 fathoms, 26.9.1962. This new species adds a genus to the New Zealand Recent fauna, although several fossil species of Pholadomya have been described. It is very close to P. pacifica Dall in all respects but appears to differ in the rather more central position of the beaks, the persistence of obsolete radials anteriorly and posteriorly of the central highly sculptured area, and in the much finer concentric sculpture. When additional material of both pacifica and maoria is available, it may well be found that these apparent differences are not significant. Living species of Pholadomya are, however, rarely encountered and the two forms are so widely separated geographically that the apparent morphological differences may be given systematic recognition.