Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 39e): holotype, GS1089, V21/f8482, Okauawa Stream, Kereru Road, Hawke's Bay, Nukumaruan (TM2207, GNS) (exterior).
(Pl. 39h): GS3339, S27/f576, Makara River, east of Martinborough, southern Wairarapa, Nukumaruan, sympatric with B. yatei (GNS) (interior).
Beu & Maxwell (1990): Chapter 15; p. 314; pl. 39 e,h.
Synonymy: Bassina parva Marwick 1927, p. 619; Circomphalus parvus Beu 2004, p. 177
Classification: Veneridae: Venerinae
Description: Very small for genus (13-21 mm long), moderately elongate, with strongly prosogyrous umbo, strongly concave and deeply impressed lunule, evenly rounded anterior end, quadrate posterior end, lightly concave posterior ventral margin but evenly convex anterior ventral margin, and a prominent angulation from umbo to postero-ventral corner. Sculpture of few, widely spaced, high, thin, frilled, commarginal lamellae, concave dorsally in cross-section, bearing short spine-like flutes down posterior ridge and another, faintly defined, radial ridge slightly behind middle of length. Interior of ventral margin finely but deeply crenulate. Hinge short, deep, strongly inclined downward towards anterior; right valve with very narrow, grooved posterior cardinal tooth, median wide, triangular one and thin anterior cardinal one parallel to lunule; left valve with long, vertical, narrow anterior cardinal tooth, stout grooved median one, and lamellar posterior cardinal fused to nymph. Adductor scars very small, subcircular. Pallial sinus deep, narrowly triangular.
Comparison: Circomphalus parvus is commonly sympatric with the much larger, more oval C. yatei (Waipipian-Recent), which lacks the median "speighti rib" of C. parvus and older species; apparently descended from the slightly larger, more inflated C. katherinae (Waipipian- (?)Mangapanian); much smaller and with closer lamellae and a weaker median radial ridge than C. speighti (Pl. 10 h; Duntroonian-Tongaporutuan). Circomphalus species are discussed in more detail under C. speighti.
Distribution: Mangapanian-Nukumaruan; Okauawa Stream, Kereru Road, inland central Hawke's Bay, Nukumaruan (type); known from one Mangapanian locality (base of sand zone upstream from rail viaduct, Mohaka River, northern Hawke's Bay; with Circomphalus yatei, Aethocola (Zelandiella) pliocenica, Pelicaria granttaylori Beu, 2009, and the early form of Struthiolaria frazeri); abundant at many Nukumaruan localities in Wanganui basin, Hawke's Bay, Wairarapa, and North Canterbury, always in shallow-water sandstone with diverse Mollusca.
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)