GNS Science

Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)

New Zealand Cenozoic Mollusca

Amalda (Gracilispira) morgani (Allan, 1926)


(Pl. 8f): GS9508, J40/f8803, McCulloch's Bridge, Kaiatan (GNS)

Beu & Maxwell (1990): Chapter 8; p. 121; pl. 8 f.

Synonymy: Ancilla morgani Allan 1926, p. 342-343; Baryspira morgani; B. (Gracilispira) morgani

Classification: Olividae: Ancillinae

Description: Size moderate for genus (height 15-26 mm), ovate, spire conical, somewhat less than half total height. Protoconch mamillate, apparently of about 1.5 whorls, but normally covered by spire callus. Teleoconch of about 4 or 5 whorls, spire whorls weakly concave to gently convex, covered by spire callus; last whorl evenly convex. No sculpture apart from growth lines. Spire callus not very thick, spreading down over upper part of last whorl, a wide uncallused area between it and the anterior callus. Depressed band (immediately above anterior callus) well defined, relatively broad. Parietal callus moderately thick, outer edge straight or gently convex from top of columella to bottom of spire callus, then bending around back of shell to eventually blend with spire callus. Aperture elongate- ovate, with moderately deep U-shaped siphonal notch; columella short, subvertical, bearing 4-7 narrow, rather irregular ridges which extend outside the aperture.

Comparison: Amalda morgani differs from other members of the subgenus Gracilispira in having a relatively broad depressed band and a parietal callus in which the outer edge is straight or gently convex rather than sigmoidal. The poorly known A. (Gracilispira) allani (Porangan?, Otaio Gorge) resembles A. morgani in having a broad depressed band, but it seems to have been taller-spired (spire more than half total height). These are the earliest species of A. (Gracilispira) recorded in New Zealand.

Distribution: Bortonian-Runangan; Kaiatan, Waihao Greensand, McCulloch's Bridge (type); Waihao Downs; Tokarahi, North Otago; Trig M, Totara, North Otago. Very common at McCulloch's Bridge, rare at other localities.

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
ISBN 978-0-478-19705-1
ISSN 1177-2441
(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)


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