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“Limatula (s. str.) vigilis Fleming n. sp.
Shell small, rather solid, oval, opaque, somewhat opisthocline, greatest length at mid height. Beaks low, rounded, rising above hinge line, which is rather short, declivous before and behind the beaks, forming upper limit of narrow ears defined by weak sub-auricular sinuses. Anterior margin rather flatly rounded, posterior more convex, ventral narrowly rounded. Median structure consisting of a radial groove in right valve, scarcely recognizable externally but represented internally by a strong flat costella margined by prominent grooves and with a strong marginal denticle; in the left valve a median rib, but rarely pre-eminent, is represented internally by a groove bordered by 2 costellae each with a strong marginal denticle; wear may reduce the prominence of the median marginal denticles. Radial ribs of rounded profile, beaded by intersection of prominent growth lines, about 12 behind and 8 in front of median rib, decreasing in strength towards the margins which have only concentric ornament, the anterior submarginal area broader than the posterior.
Dimensions: length 3.3, height 5.5, inflation 2 mm (holotype, right valve); length 4.5, height 7.5, inflation 2.5 mm (largest paratype, Mernoo Bank, National Museum M 15398).
Holotype: TM 5492, N.Z. Geological Survey, 39 fm (75 m) in Narrow Bend, Long Sound, Preservation Inlet (New Golden Hind Station B3).
Localities: N.Z.O.I. D38, 7 May 1963, 188-252 m, 51° 58’ S, 165° 28’ E, Auckland Islands Ridge, south of Auckland Islands; 19 and 71 m, east of Auckland Islands (N.Z.O.I. D60, D103; 1963); 50 fm (95 m) off the Snares Islands (Suter Collection, J. Bollons); 161 m off Snares Island (N.Z.O.I. D100, 26 September 1963); 84 m, 47° 10.5’ S, 167° 28.5’ E, off west coast of southern Stewart Island (N.Z.O.I. A 842, 26 August 1963); 105 m, 47° 15’ S, 168° 15’ E, off east coast of southern Stewart Island (N.Z.O.I. A 855, 28 August 1963); 39 fm (75 m), Narrow Bend, Long Sound, Preservation Inlet (type locality as above); Dusky Sound, 60 m (National Museum M 6610. Coll. R. Henry); BS 106, 10 m, between unnamed and Breaksea Island, Breaksea Sound (National Museum, M 13820, W.H. Dawbin, M.V. Alert); 141 m Veryan Bank, 44° 18’ S, 176°10’ E (N.Z.O.I. D 1, 12 April 1963); Chatham Islands Expedition Stn. 3, 41 fm (80 m), Mernoo Bank (National Museum M 15398 and N.Z. Geological Survey); BS 164, Alert, station B, 62 fm (120 m), west of Kapiti, Cook Strait (National Museum M 16219); 77 m, east of Cape Palliser (N.Z.O.I. C 842, March 1962); 21 m, Wellington Harbour (N.Z.O.I. D 343, 19 November 1964); 38 fm (75 m) off Cuvier Island, Hauraki Gulf (National Museum M 6613, J. Bollons); AUZ 53, 805 m (440 fm), north of Three Kings Islands (National Museum M 58 340).
Remarks: This form was classed as L. suteri by Suter and some more recent National Museum curators and as L maoria in the Geological Survey collection. Juvenile L. maoria has narrower beaks, straighter hinge line, more narrowly triangular ribs, and weaker median structure and marginal denticles. L. vigilis differs from L. acherontis in its narrower (i.e. shorter) shell and more numerous ribs, from L. tensa in its fewer ribs, which evanesce on the submargins, and from L. siligo n. sp. in its more oval shape and more numerous ribs.
The species name is the genitive of the substantive form of the adjective vigil (awake, watchful, alert) and is chosen to commemorate the pioneer dredging expeditions of Mr. A.J. Black in his harbor-defence motor launch, the “Alert”.”