Go to National Library of New Zealand Te Puna Mātauranga o Aotearoa
Volume 38, 1905
This text is also available in PDF
(2 MB) Opens in new window
– 285 –

17. Pleurotoma (Hemipleurotoma) alticincta, n. sp. Plate XXII, figs. 12, 13.

Shell small, turriculate, subcylindrical, with a long spire, deeply sulcate whorls, an oblong aperture which is slightly shorter than the spire, and a short canal. Sculpture: On the upper spire-whorls a few minute spiral striæ, the next with four distinct cinguli, on the succeeding a minute fifth spiral arises at the suture, which on the penultimate strengthens and about equals the adjoining revolving ribs; the cinguli are strong, rounded and adorned with minute spiral threadlets, absent in the grooves; the latter are deep, somewhat square-cut, and narrower than the ribs; the last whorl with ten ribs and a number of minute threadlets upon the back of the canal, added to which are the oblique lines of old beaks; grooves and ribs about equal, but the former sometimes broader as they proceed anteriorly. The longitudinal growth-striæ are minute, slightly irregular in strength, and giving in places (usually upon the upper whorls of the spire) a slightly clathrate appearance. Colour: There is only one young specimen that has a somewhat fresh appearance, it is light horn-coloured; all the others are greyish-white. Spire long, gradate, turriculate, with an obtuse rounded apex. Protoconch of about two convex turns, slopingly shouldered, with minute spirals the precursors of the adult sculpture; nucleus central, depressed-globular, smooth. Whorls 7, flattened, strongly shouldered at the suture, first slowly then more rapidly increasing, the last a little longer than the spire. Suture deep, margined above on the lower whorls. Aperture elongate, somewhat narrow, slightly contracted in front and forming a short open canal, which is truncated and slightly sinuate at the base, bent backward and a little to the left. Outer lip slightly thickened, descending with a light downward sweep, crenulate on the margin; the sinus indistinct, situated on the uppermost cingulum. Inner lip forming a broad callus through which on the body the three cinguli appear as folds, with a distinct edge, which is slightly raised, connected above with the outer lip; columella excavated in

– 286 –

the middle, drawn out to a point on approaching the anterior beak. Altitude, 15·7 mm.; diameter, 5·75 mm.

Type in the Colonial Museum, Wellington.

Obs. This species is in its sculpture nearly allied to P. septemlirata and trilirata, Harris, from the Eocene of Australia. Three perfect specimens, one not quite adult, and a number of fragments, were obtained, all dead shells.