Bathytoma wairarapaensis n.sp. (Pl. 25, fig. 5.)
Shell of moderate size. Spire probably less than the height of the aperture plus canal. Protoconch and early whorls missing. Suture just below peripheral keel, descending on latest whorls. A single narrow, moniliform subsutural cord, the gemmules elongated transverse to the cord, in places extending up to the suture, causing it to be finely crenulated. Shoulder narrow, deeply concave, bearing numerous fine irregular spiral threads. On the peripheral keel a single raised cord ornamented with about 32 gemmules a whorl, elongated parallel to the cord. Below the periphery, early spire whorls carry a weakly gemmate cord; a second slightly stronger cord appears on later spire whorls as the suture descends. On the body whorl, 6 widely spaced narrow gemmulate cords with 6 to 8 fine irregular threads between each pair. On the neck at least 8 more closely spaced but weaker cords with irregular gemmules and a few irregular intermediate threads. The tip of the neck is broken off.
Height, 27 mm.; diameter, 15·5 mm.
Locality: N162/604, Middle Te Wharau beds, south branch of Whakatahine Stream, upper Clifdenian or Lilburnian (holotype and 1 juvenile paratype).
Since the protoconch has not been seen, the generic location is provisional It seems to be related to B. mitchelsoni Powell which differs in having the suture immediately below the periphery in all whorls, the peripheral cord double, the body whorl less inflated contracting below the keel, whereas in wairarapaensis the body whorl is at first cylindrical, then contracts rapidly. The two species also differ in minor details of the ornament.
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Of moderate size, narrowly biconic, spire slightly higher than aperture plus canal. Protoconch small, dome-shaped, of 1 1/2 smooth whorls. 6 post-nuclear whorls regularly increasing in size. Sculpture, peripheral keel with 16 to 17 strong nodules; subsutural cord with an equal number of nodules, about half the size and slightly in front of the peripheral nodules. Shoulder narrow, concave, with 2 weak spiral threads. Body whorl, below the periphery, with 3 strong spaced gemmate cords, with single interstitial threads, followed by 6 fine threads on the neck; the 3 strong moniliform cords are present in all paratypes, but the finer sculpture on the body whorl is variable.
Height, 13 mm.; diameter, 6 mm.
Localities: N165/508, N165/507 (holotype), Bell's Creek, middle Tongaporutuan. This species is not closely related to other described species of Micantapex.
Micantapex murdochi prior n.subsp. (Pl. 26, fig. 12.)
Differs from murdochi chiefly in having larger and fewer peripheral nodules: holotype and one paratype 16, one paratype 15 and one paratype 14 nodules per whorl. Keel closer to the lower suture than in murdochi. Sub-sutural cord weak, with numerous weak nodules. Base and upper part of neck, with 9 spaced, narrow, raised cords, 1 intermediate between the fifth and sixth counted from above; 7 finer closer cords on lower part of neck, and fasciole.
Height, 20 mm., diameter, 9 mm.
Locality: N162/717. Blue-grey, silts immediately below shell limestone, Wheraiti Hill, on Te Wheraiti-Fernyhurst Road, top of Pelicaria acuminata zone (lower Nukumaruan); holotype and 3 paratypes.
This form may merit specific separation, but as yet only four specimens are known. It is very similar to murdochi in general appearance, but the differences seen on closer inspection are constant. The new subspecies seems to be intermediate in some characters between murdochi and proavitus Powell, having the narrow, weakly nodulous sub-sutural border of the latter, relatively fewer nodules on the keel, and the keel set lower on the whorl than on murdochi. No paratype has any trace of interstitial spiral sculpture such as is typical of murdochi and proavitus.