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Volume 79, 1951
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New Marine Mollusca from the Cook Strait Area and
Southern New Zealand

[Read before the Wellington Branch, October 24, 1950; received by the Editor, October 24, 1950]

In November, 1936, the N.Z.G.S. Matai, in the course of a preliminary survey of the Mernoo Bank (approximately 90 miles N. 63°E. of Godley Head) obtained a number of bottom samples, which by courtesy of the Marine Department were deposited in the Dominion Museum. A number of species have been sorted out as new and are described below. A full species list and discussion of the sediment will be published elsewhere (Dell, in press). One new species, Venustas benthicola has already been described from this area (Dell, 1950, p. 47).

In addition, a new genus and species of Rissoid from Foveaux Strait and a new Mysella from the Chatham Islands are also described in this paper.

The writer is indebted to Mr. C. A. Fleming for permission to describe the Foveaux Strait Rissoid. The drawings for Plate 85, figures 1 and 4, were made by Miss S. Traill, of the Dominion Museum staff.


Genus Perrierina Bernard, 1897
Type (by monotypy): Perrierina taxodonta Bernard

Perrierina subquadrangula n.sp. (Pl. 84, figs. 2 and 5)

Shell small, inequilateral, inflated, ovoid-quadrangular; beaks low with slightly raised prodissoconch. Surface smooth and shining with occasional indistinct growth lines. Colour very light brown with darker patches of reddish brown. Dorsal margin arched posteriorly, dropping suddenly in behind, somewhat flattened antero-ventrally, rounded in front. Hinge of usual type for genus. Right valve with two strong divergent cardinals united above, posterior tooth grooved slightly. Lateral lamellae well represented, six posteriorly, four anteriorly.

Length, 1·8 mm.; height, 1·4 mm.; inflation (one valve), 0·66 mm.

Locality: Mernoo Bank, 43° 21′S., 175°E., in 52 fathoms. N.Z.G.S. Matai, 6/11/36.

Holotype (M.5497) in Dominion Museum.

Differs from all the described species in outline and in lacking distinct radials. This is the first record of the genus from the Cook Strait area, though species have been recorded from the Aupourian and Forsterian and from the Chathams.


Genus Condylocardia Bernard, 1896
Type: Condylocardia sanctipauli Bernard

Condylocardia mernoo n.sp. (Pl. 84, fig. 1)

This species is closest to C. torquata Marwick, described from a right valve from the Pliocene of the Chatham Islands. Powell (1933,

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p. 190) has recorded torquata as occurring Recent at the Chathams and has given more details of the hinge characters.

The Cook Strait population differs in the considerably smaller size (though obviously mature) and in shell outline and is therefore described as new. The Chatham Island Recent shell may well be different.

Shell very small, white, obliquely ovate-trigonal, posterior end produced, anterior truncated. Surface sculptured with fine concentric ridges, every third or fourth heavier. Prodissoconch large, bounded by a raised collar produced into a projecting knob posteriorly. Left valve with two cardinals attached near the beaks and diverging proximally. The posterior cardinal slopes obliquely forward, the anterior practically vertical. Right valve with two cardinals, the anterior cardinal being stout and short, the posterior set obliquely and being thinner and more lamellar in structure.

The laterals appear to be derived from the shell margin, there being two in each valve. In the right valve a socket is left between the lateral and the shell margin anteriorly. The hinge formula may be indicated as follows, for comparison with Powell's formula for Recent Chatham Island torquata:

 L. 10 . 10 r 10 . 10 = 2 cardinals and two laterals.

R. 01 . 01 r 01 . 01 = 2 cardinals and 2 laterals.

Height, 1·1 mm.; length, 1·3 mm.; inflation (one valve), 0·4 mm.

Locality: Mernoo Bank, 43°21′S., 175°E., in 52 fathoms. N.Z.G.S. Matai, 6/11/36.

Holotype [two disconnected valves] (M.5498) and 12 paratypes (M.5499) in Dominion Museum Collection.

Differs from torquata in the smaller size and more trigonal outline and from Recent Chatham Island shells in the development of two laterals in the right valve.


Genus Mysella Angas, 1877
Type (by monotypy): Mysella anomala Angas

Mysella lachlani n.sp. (Text fig. 1)

Picture icon

Text Fig. 1—Mysella lachlani n.sp. Holotype. 6.1 × 5.2 mm.

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Shell of moderate size for genus, oval, inequilateral, white, fairly thin. Beaks posterior. Outline ovoid, produced and expanded anteriorly. Hinge of right valve with two divergent cardinals separated by the resilium, the dorsal edge of the shell being raised into a lateral lamella anteriorly. Surface with numerous irregular concentric growth striae.

Height, 6·1 mm.; length, 5·2 mm.; inflation (single valve). 1·22 mm.

Locality: Mernoo Bank, 43°21′S., 175°E., in 52 fathoms. N.Z.G.S. Matai, 6/11/36.

Holotype [a single right valve] (M.5500) in Dominion Museum, Wellington.

Appears to belong to the beta-henryi group. Named after H.M.N.Z.S. Lachlan, whose recent survey of the Mernoo Bank has added much to our knowledge of its topography.

Mysella hounselli (Powell) (Pl. 84, fig. 3)

1931. Virmysella hounselli Powell, Rec. Auck. Inst. Mus., Vol. 1, p. 111.

Originally described from the Castlecliffian (Upper Pliocene) the writer has recorded this species from 25 fathoms, off White Rocks, Queen Charlotte Sound, and there are specimens from 85 fathoms off Poor Knights in the N.Z. Geological Survey Collection. Figures are here given of a left and right valve from Queen Charlotte Sound.

Mysella morioria n.sp. (Pl. 84, fig. 4)

Shell comparatively large for genus, elongate-oval, thin, white. Beaks somewhat posterior. Outline elongatedly oval with beaks produced dorsally, anterior margin produced, rounded, posterior margin broadly rounded. Hinge in right valve with two comparatively large, divergent cardinals separated by the resilium. In the left valve the shell margins are produced into two well-marked lamellae, anteriorly and posteriorly situated respectively. Proximally these lamellae are produced and thickened to take on the nature of true teeth and interlock with the cardinals of the right valve. Colour white. Surface with fairly regular, well-marked concentric ridges between which three or four weak concentric striae are developed. Between this concentric sculpture fine, regular, disconnected radials are developed over the lower third of the shell. The central portion of the shell is rather irregularly pitted between the concentric sculpture, giving an unusually characteristic surface.

Length Height Inflation (single valve)
Holotypo (right valve) 7.4 5.5 1.1
Paratype (left valve) 7.0 5.4 1.02
Paratype (right valve) 7.0 5.2 1.18

Locality: Chatham Islands.

Holotype (M.5501) collected by W. Taylor, in Dominion Museum, Wellington, paratypes (right and left valves) in collection of N.Z. Geological Survey, Wellington.

The described species from New Zealand waters with their known distribution are as follows:

M. unidentata (Odhner). Stewart Island (type), Fiordland; off the Bounty Islands; Chatham Islands; Cook Strait.

Picture icon

Fig. 1—Condylocardia mernoo n.sp. Holotype. 1.1 × 1.3 mm.
Figs. 2, 5—Perrierina subquadrangula n.sp. Holotype. 1.8 × 1.4 mm.
Fig. 3—Mysella hounselli (Powell). 25 fathoms, Queen Charlotte Sound.
Fig. 4—Mysella morioria n.sp. Holotype. 7.4 × 5.5 mm.

Picture icon

Fig. 1—Ruapukea carolus n.gen. et n.sp. Holotype. 1.5 × 0.7 mm.
Fig. 2—Coenaculum tertium n.sp. Holotype. 1.74 × 0.4 mm.
Fig. 3—Lironoba matai n.sp. Holotype. 1.18 × 0.72 mm.
Fig. 4—Ciosseola cookiana n.sp. Holotype. 1.1 × 1.2 mm.

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  • M. macquariensis (Hedley). Macquarie Island.

  • M. charcoti (Lamy). Macquarie Island.

  • M. aupouria Powell. Off Three Kings Islands.

  • M. alpha Powell. Off Three Kings Islands.

  • M. beta Powell. Off Three Kings Islands.

  • M. tellinula (Odhner). North Cape, littoral.

  • M. larochei Powell. Whangaroa; Tom Bowling Bay.

  • M. henryi Fleming. Fiordland (type); Stewart Island.

  • M. hounselli (Powell). Queen Charlotte Sound, 25 faths.; Poor Knights, 85 fathoms; Castlecliff, Wanganui (Castlecliffian).

  • M. lachlani n.sp. Mernoo Bank, Cook Strait, 52 fathoms.

  • M. morioria n.sp. Chatham Islands.

The only fossil species recorded apart from hounselli is:

M. apudalpha Laws. Altonian. Pakaurangi Pt.

The classification of these rather featureless Leptonids is difficult. Practically every area whose molluscan fauna has been investigated at all thoroughly in recent years has provided at least one, and in some cases several new species of Mysella, yet none of the dozen described species can satisfactorily be given subspecific rank. The species beta, lachlani, and henryi may form one series and perhaps unidentata and hounselli another.

M. morioria has a different type of sculpture from the rest of the species and might perhaps better be placed in Rochefortula. The sculpture is, however, not identical with that found in that genus and the other characters appear to agree rather with Mysella. Apparently the largest species of the genus yet recorded from New Zealand.


Genus Crosseola Iredale, 1924
Type (o.d.): Crossea concinna Angas

Crosseola cookiana n.sp. (Pl. 85, fig. 4)

Shell small, white, solid, turbinate-depressed, perforate. Whorls 3½ including small smooth protoconch of one whorl. Sculpture of moderately strong spiral cords crossed by axials of sub-equal strength. Two strong spirals on spire whorls, five and umbilical cord on body whorl; the upper three above the aperture most prominent. Axial lamellations well developed, spacing variable, forming hexagons with the spirals, becoming lamellar across the base. Spire depressed, a little more than half the height of the aperture. Aperture circular, peristome continuous, thickened. Umbilicus comparatively wide, width about one-eighth the greatest diameter, deep, bounded by a strong, crenellated, umbilical rib.

Height, 1·1 mm.; diameter, 1·2 mm.

Locality: Mernoo Bank. 43°21′S., 175°E., in 52 fathoms (holotype); 43°24’S., 175°18’E., in 57 fathoms (paratypes), N.Z.G.S. Matai, 6/11/36.

Holotype (M.5502) and two paratypes (M.5504) in Dominion Museum.

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From the four described species from New Zealand waters, errata Finlay, cuvierensis Mestayer, favosa Powell and intertexta Powell, the new species differs in the depressed outline and comparatively wide umbilicus. It is close to errata Finlay in sculptural details and in possessing an umbilicus and it may be a regional representative. Until the distribution of our small marine mollusca is better known, however, it is best treated as a full species.


Genus: Coenaculum Iredale, 1924
Type (o.d.): Scalaria (Acrilla) minutulum Tate and May

Coenaculum tertium n.sp. (Pl. 85, fig. 2)

Shell small, slender, cylindrical, white. Whorls 4 1/2 including a large protoconch of 1 1/2 whorls. Spire tall, 2 1/2 times the aperture height. Spire whorls slightly angled above the middle. Body whorl also angled at the level of the aperture. Protoconch at first smooth, at the end of the first half whorl a prominent, median spiral keel is developed, over the last whorl two strong spiral keels are developed together with a very faint supra-sutural thread. Post-nuclear sculpture of thin flexuous axials which gradually become obsolete after crossing the sutural angulation on the body whorl. There are about 20 axials on the body whorl. Axials retracted across the shoulder of the whorl. Aperture quadrate. Peristome thin, flexuous, sigmoid in profile, a broad, moderate deep sinus at the angle. Columella straight

Height, 1·74 mm.; diameter, 0·4 mm. (holotype).

Locality: Mernoo Bank, 43°21′S., 175°E., in 52 fathoms. N.Z.G.S. Matai, 6/11/36.

Holotype (M.5505) and single broken paratype (M.5506) in Dominion Museum.

The damaged paratype has diameter 0·8 mm., so the species probably grows to twice the size of the holotype. This is the third known species of the genus. The genotype, minutulum (Tate and May) is recorded from Tasmania and New South Wales, and secundum (Powell) was described from off the Three Kings Islands. The relationships of the three species is best shown in a key.

Key to the Species of Coenaculum

1.Protoconch with three spiral keels, sutural keel on body whorl well developed. Spire whorls with strong median angulationminutulum
2.Protoconch with one spiral keel, sutural keel on body whorl well developed. Spire whorls with slight supramedian angulationsecundum
3.Protoconch with two spiral keels and faint third thread, sutural keel not present, but body whorl markedly angled. Spire whorls with slight supramedian angulationtertium

Genus Lironoba Iredale, 1924
Type (o.d.): Rissoa suteri Hedley

Lironoba matai n.sp. (Pl. 85, fig. 3)

Shell small, elongately conical, white, solid, with well-marked spiral ridges. Whorls 4 1/2 including a smooth rounded protoconch of 1 1/2 whorls. Spire about 1 1/2 times the height of the aperture. Protoconch under medium magnification smooth, but seen to be minutely pitted under

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higher powers. Post-nuclear sculpture consisting of two strong, raised, spiral ridges of approximately equal development. Body whorl with an additional spiral ridge above the aperture and three weaker ridges across the base. Ridges and interspaces crossed by fine, very weak incised axials. Aperture ovate, peristome continuous, smooth. Parietal callus separated from body whorl by a narrow groove.

Height, 1·18 mm.; diameter, 0·72 mm.

Locality: Mernoo Bank, 43°21′S., 175°E., in 52 fathoms. N.Z.G.S. Matai, 6/11/36.

Holotype (M.5507) and five paratypes (M.5508) in Dominion Museum.

Superficially this species would be taken to be a Nobolira, it being very close to manawatawhia Powell and hinemoa Fleming. The protoconch has no sign of any spirals in any of the specimens and the species must be placed in Lironoba. The axials, though only slightly developed, are another link with suteri, the genotype. Laseron (1950, p. 263) has recently questioned the advisability of continuing to use the characters of the protoconch in hard and fast generic diagnoses in the Rissoidae. We have in this family in New Zealand several pairs of genera (e.g. Lironoba and Nobolira, Merelina and Linemera) which are separated upon apical characters and the situation may require investigation. It would be advisable (in this family) to use additional diagnostic characters when distinguishing closely allied genera rather than relying on the protoconch alone.

Genus Ruapukea nov.
Type (o.d.): Ruapukea carolus n.sp.

Small, colourless and sculptureless Rissoids are notoriously difficult to place generically. The specimen upon which this genus is based does not agree with any Australasian Rissoid genus.

The chief diagnostic features are the cylindrical shape, smooth, glassy protoconch and general shell surface, the extremely convex shell outline and the round semi-entire aperture with expanded outer lip. Other characters those of the genotype.

Ruapukea carolus n.sp. (Pl. 85, fig. 1)

Shell small, cylindrical, glossy, white, with tall spire, twice the height of the aperture. Whorls 4 1/2 including the protoconch. Protoconch smooth, glossy and globose, exact limits not well defined. Outline of whorls strongly convex, sutures deeply impressed. Only sculpture consists of irregular growth wrinkles. Aperture circular, peristome continuous, reflexed all round and thickened internally, joined to the parietal wall for short area only. Separated from body whorl by a narrow chink.

Height, 1·5 mm.; diameter, 0·7 mm.

Locality: 13 fathoms off Ruapuke Island. Foveaux Strait. Collected by C. A. Fleming, to whom I am indebted for permission to describe this interesting form.

Holotype in collection of N.Z. Geological Survey.

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Dell, R. K., 1950. The Molluscan Genus Venustas in New Zealand. Dom. Mus. Rec. Zool., vol. 1, no. 5, pp. 39–54.

—– (in press). A Molluscan Fauna from the Mernoo Bank.

Laseron, C. F., 1950. Review of the Rissoidae of New South Wales. Rec. Aust. Mus., vol. 22, no. 3, pp. 257–287.

Powell, A. W. B., 1931. Waitotaran Faunules of the Wanganui System. Rec. Auck. Mus., vol. 1, no. 2, pp. 85–112.

—– 1933. The Marine Mollusca of the Chatham Islands. Rec. Auck. Mus., vol. 1, no. 4, pp. 181–208.

—– 1937. New Species of Marine Mollusca from New Zealand. Discovery Reports, vol. 15.