Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 22u): Bluecliffs, Otaio River, Otaian (Canterbury Museum)
Beu & Maxwell (1990): Chapter 11; p. 208; pl. 22 u.
Synonymy: Terebra biplex Hutton 1885b, p. 327
Description: Size moderate for genus (height 20-30 mm), turriculate, spire elevated. Protoconch narrowly conical, of about 5 convex whorls, last quarter-whorl with narrow opisthocyrt costellae, remainder smooth. Teleoconch of 8-10 whorls, early whorls narrowly concave posteriorly, convex below; later whorls swollen at both ends, flat or slightly concave between; last whorl with prominently angled periphery, convex base and short neck. Axial sculpture of narrow, sharp-crested costae that are more prominent on swellings than between, and are typically nodular on peribasal angulation. Costae reaching from suture to suture on spire, but scarcely extending onto base; 12-16 costae on penultimate whorl. Spiral sculpture apparently absent from early whorls, consisting on later whorls of numerous closely spaced threads over whole surface. Aperture with short, notched siphonal canal; fasciole prominent, ridge-margined. Columella vertical posteriorly, twisted to left below. Outer lip broadly and shallowly concave between suture and periphery, almost straight below.
Comparison: Zeacuminia biplex is distinguished from other species of Zeacuminia by having a prominent subsutural swelling and a slightly less prominent suprasutural swelling, and in having relatively few, sharp-crested axial costae that are considerably stronger on swellings than in between. Z. planitas (Opoitian-early Nukumaruan; Pl. 37z) is closest, but the costae become obsolete between the swellings on adult whorls, leaving two rows of prominent nodules.
Distribution: Otaian; "Pareora" (type probably from Mount Harris Formation, foot of Mt Horrible, Pareora River); Bluecliffs, Otaio River, moderately common.
Cite this publication as: "A.G. Beu and J.I. Raine (2009). Revised
descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990). GNS
Science miscellaneous series no. 27."
© GNS Science, 2009
(Included with a PDF facsimile file copy of New Zealand Geological Survey Paleontological Bulletin 58 in CD version from: Publications Officer, GNS Science, P.O. Box 30368 Lower Hutt, New Zealand)