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Key to Geographical Ranges
The symbols K.A.C.F.M.An. are used to indicate the geographical range of the species. They have been adopted to give an approxomation of the range of each species within New Zealand.
Kermadec Islands
Aupourian - Kaipara Harbour, north around North Cape, encompassing the Three Kings Islands and south to East Cape
Cookian - Lower North Island and the northern part of the South Island
Forsterian - Otago, Fiordland and Stewart Island
Moriorian - Chatham Islands, Pitt Island
Antipodean - Subantarctic Islands of New Zealand
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Bivalvia - Heterodonta - Veneroida - Family: Mactridae

Mactridae: Mactrinae


Genus: Crassula

Crassula aequilatera (Deshayes, 1854) (=aequilateralis Deshayes)
Length 75mm, Height 55mm, Diamond Surf Clam. Endemic
North, South and Stewart Island. In shallow water off sandy beaches [ACFE.]

Genus: Cyclomactra

Cyclomactra ovata (Gray, 1843)
Length 80mm, Height 62mm, Endemic
North, South and Chatham Islands. Buried deeply in soft mud [ACFME.]
Cyclomactra tristis (Reeve, 1854)
Length 60mm, Height 55mm, Endemic
North Island. Buried in mud at low tide [ACE.]

Genus: Mactra (Maorimactra)

Length 15mm, Height 10mm, Endemic. Sculpture of very fine and dense concentric lirations, slightly stronger at the sides. Distinguished from juvenile discors by the lack of a posterior ridge
North Island and northern half of South Island. In mud in shallow water [ACE.]

Genus: Oxyperas

Oxyperas belliana (Oliver, 1915)
Kermadec Islands [K.E.]
Oxyperas elongata (Quoy & Gaimard, 1835)
Length 110mm, Width 65mm, Endemic
North, South, Stewart and Chatham Islands. Shallow water to over 70 metres [ACFME.]

Genus: Scalpomactra

Length 30mm, Height 19mm, Endemic
North, South, Stewart and Chatham Islands [ACFE.]

Genus: Spisula (Spisulona)

Height 80mm, Length 90mm, Thickness 45mm, Large Trough Shell. Endemic. Darker, more inflated than Mactra murchisoni. Colour white under a dark brown periostracum
North, South and Stewart Island [ACFE.]
Width 85mm, Height 70mm, Endemic. Wider, less inflated than Mactra discors. More laterally ovate, inequilateral, has transverse plications on the lateral teeth, and the periostracum is always pale straw colour
North, South and Stewart Island. On exposed sandy beaches [ACFE.]

Mactridae: Lutrariinae


Genus: Lutraria (Psammophila)

Off Kermadec Islands [K.E.]

Mactridae: Zenatiinae


Genus: Resania

Resania lanceolata Gray, 1852
Length 100mm, Height 48mm, Lance Mactra. Endemic
North and South Islands. Off sandy ocean beaches in shallow water [ACFE.]

Genus: Zenatia

Zenatia acinaces (Quoy & Gaimard, 1835)
Length 100mm, Height 46mm, Endemic
North and South Islands. Off sandy beaches in shallow water to about 50 metres [ACFE.]