Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
| | Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990) |
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  (Pl. 34d): GS3528, R11/f7014, Otahuhu Brewery well, Auckland, Waipipian (TM4701, GNS) |
 (Pl. 34g): GS3528, R11/f7014, Otahuhu Brewery well, Auckland, Waipipian (TM4701, GNS) |
Beu & Maxwell (1990): Chapter 14; p. 285; pl. 34 d, g.
Synonymy: Eumarcia kaawaensis Marwick 1927, p. 627; Eumarcia (Eumarcia) kaawaensis, Beu & Maxwell 1990, p. 285, pl. 34d, g.
Classification: Veneridae: Tapetinae
Description: Moderately large for genus (80 mm long), evenly elongate-oval; slightly taller, more inflated, and more trigonal than E. plana (Pl. 40g h); umbones higher, more inflated, and much more prominent than in E. plana. Exterior polished, smooth except for irregular commarginal folds that are quite prominent on some specimens. Lunule slightly depressed, otherwise poorly defined. Hinge relatively short, with 3 cardinal teeth in each valve, all narrow and protruding well, 2 of them bifid in each valve; end of nymph slightly raised in left valve to form a very small, narrow posterior lateral tooth, with corresponding weak socket beyond nymph end in right valve. Anterior adductor muscle scar deeply impressed; anterior pedal retractor muscle scar a small, deeply excavated depression just above adductor, embaying hinge margin; posterior adductor muscle scar slightly larger than and much more shallowly impressed than anterior one. Pallial sinus relatively short, margins parallel, apex rounded to obliquely truncated. Interior of ventral margin smooth, polished.
Comparison: Similar large, almost smooth forms similar to (and presumably ancestral to) Eumarcia plana (Pl. 40g, h) but having higher, more inflated umbones, are known also from Tongaporutuan rocks in North Taranaki and southern Wairarapa. E. kaawaensis differs from E. plana mainly by its much greater inflation and its larger, more nearly central umbones. The small left posterior lateral tooth is unique among New Zealand Eumarcia species. All these species are larger and considerably more inflated than E. pareoraensis (Altonian, Southburn Sand facies of South Canterbury). Eumarcia and Atamarcia are now considered to be distinct genera.
Distribution: Opoitian-Waipipian; Kaawa Creek, southwest Auckland, Opoitian (type); also recorded from Otahuhu Brewery well, Auckland, Waipipian (Marwick 1948). Both localities are shallow-water, near-shore shellbeds.
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)