“Maorithyas marama n.sp. (Plate 25, fig. 2)
1913. Thyasira flexuosa Mont. Suter, Man. N.Z. Moll. P. 919 (in part); Atlas, pl 63, fig. 11 (not of Montagu, 1803).
Shell white, chalky without, shining within, sub-spherical, globosely-inflated, with low beaks directed forwards. A shallow but well-defined sulcus runs from beak to posterior margin and an obsolete fold and sulcus anteriorly. Dorsal margin arched, descending in front and behind, posterior margin indented at sulcus, ventral and anterior margin broadly rounded. Sculpture of irregular growth folds, locally anastomosing. Hinge plate thin and delicate, anterior part tapering backwards to behind beak, where it is overlapped by the posterior part, which widens backwards and is excavated to form a ligamental groove tapering forwards beneath the beak, bounded by a ridge-like nymph below; a crescentic narrow escutcheon on both valves extends from below the beak to the posterodorsal angle. Lunule broad, semi-circular, defined by a low told over which growth folds are flexed. Interior shining, with well-marked, fine, irregular radial striae, which do not crenulate the margin. Muscle scars indistinct; anterior somewhat rounded, with a small pedal scar above it, posterior rounded trigonal.
Length 18; height; 17; inflation (both valves) 13.5 mm. (holotype).
Length 13.5; height 14.2; inflation (1 valve) 50 mm. (valve figured by Suter).
Localities: Fiordland; several localities, type from Suter collection, and many paratypes. The type is from 12 fathoms, Wet Jacket Arm, and valves are not uncommon in New Golden Hind dredgings from 2 to 58 fathoms. Anchorage, of mouth of Crooked Reach, Port Pegasus, in 5 fathoms. "Alert" expedition, November 23rd, 1947 (Dominion Museum and Geological Survey Collections). Also at Waikanae Beach, Wellington, North Island; several specimens, accompanying T. peroniana waikanae, n. subsp., in the Dominion Museum.
Suter had this species labelled " Thyasira flexuosa Mont.," and the actual valve used to illustrate flexuosa (Atlas, pl. 63, fig. 11) has been identified in the series from 12 fathoms, Wet Jacket Arm. There is a related form in dredgings made by the writer at the head of Deep Inlet, Auckland Islands, which will be dealt with by Mr. A. W. B. Powell in a report on subantarctic mollusca now being prepared. Small specimens of Maorithyas are with difficulty separated from Genaxinus otagoensis (Suter) and the affinity of otagoensis with Maorithyas may be closer than the generic separation here adopted suggests.”
(Fleming, 1950: 253-254)
