Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 13c): GS3600, F46/f8492, Mataura River, near Brydone, Southland, Waitakian (GNS)
Beu & Maxwell (1990): Chapter 10; p. 150; pl. 13 c.
Description: Large for genus (height 12-18 mm), trigonal, strongly inflated, strongly inequivalve, right valve much the larger. Escutcheon on right valve only, large and deeply impressed. Posterior area on right valve narrow with a shallow median furrow. Sculpture on right valve of prominent, rounded commarginal costae of variable spacing, weakly sinuous on flanks on some shells; considerably weaker and more numerous (mainly as a result of bifurcation) on posterior area. Commarginal sculpture on left valve, apart from growth lines, absent or confined to small area on umbo; radial sculpture of a few feeble ridges. Right hinge with a large peg-like anterior cardinal tooth and a deeply impressed resilifer behind. Left hinge with a prominent, narrowly triangular chondrophore divided in 2 by a longitudinal ridge, and a deep socket behind chondrophore to take the right cardinal tooth. Adductor muscle scars large, subequal, anterior scar ovate, posterior one circular, pallial sinus very shallow.
Comparison: The new (?) species is very similar to the widespread Notocorbula humerosa (Duntroonian-Kapitean) but is much larger, has a more prominent radial furrow on the posterior area, and has a larger and more strongly impressed escutcheon. N. humerosa is characteristically only 7-8 mm in height. It is unclear, however, if the Waitakian form is really a distinct species or merely an unusually large variant of N. humerosa, which for some reason is restricted to this stage. Caestocorbula n. sp. (Pl. 7j, k) is also similar, but is smaller and more elongate, and has a siphonal plate.
Distribution: Waitakian; Chatton Formation, Brydone, Mataura River; Otekaike Limestone, Trig Z, Otiake; Campbell Park School, Otekaike; Brother's Stream and Sister's Creek, Hakataramea; Mount Harris Formation, upper Tengawai River.
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)