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Volume 69, 1940
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A Review of the Tertiary and Recent Neozelanic Pyramidellid Molluscs. No. 6—The Genus Odostomia.

[Read before the Auckland Institute, November 18, 1938; received by the Editor, November 29, 1938; issued separately, September, 1939.]

The Odostomid Group Of Genera.

The Odostomid group of genera comprises those with few whorls, a not greatly elevated spire, a single columella-fold, and a typically depressed embryo. The sculpture varies from shells devoid of all ornamentation to those with either axial ribs or spirals, or with both.

The Odostomid group of genera can be divided into three subgroups, as follows:—

  • Odostomia and allied generic groups (Odostomids).

  • Pyrgulina and allied generic groups (Pyrgulinids).

  • Evalea and related genera.

Odostomids.

This division embraces Pyramidellids of only moderately high conic habit, few whorls, and a single columella-fold. The embryo is usually considerably immersed, and not as exsert as that of Turbonilla or Syrnola. Axial sculpture other than growth-lines is not present; and strong, regular, universal spiral ornamentation is not a feature of the group, though fine microscopic striae or threads may be present. If spiral sculpture stronger than microscopic striae or threads is developed, it takes the form of an incised line bordering the suture, or, as in the case of Scalenostoma, Cyclodostomia, and Doliella, of one or two tumid bands or keels.

New Zealand species fall under seven genera, of which three are new. The present paper deals only with the genus Odostomia, which is divided into two groups:—

(1) Nucleus evident, helicoids Odostomia A.
(2) Nucleus not projecting Odostomia B.

A key to the genera, also tables of stratigraphic range of genera and species will be given in a later number.

The earliest Odostomid in the New Zealand area is “Odostomia sp.” (known from a single specimen) recorded by Finlay and Marwick from beds of late Cretaceous age at Boulder Hill, Dunedin (N.Z. Geol. Surv. Pal. Bull., no. 15, p. 66, pl. 5, fig. 6, 1937). In Ototaran beds three species of Odostomia A are represented, none of which is strong in individuals, however. Thereafter, in the Hutchinsonian (Upper Oligocene) five species occur, but, with the exception of O. obstinata n.sp., which is a strong species and which persisted into the Miocene, the Hutchinsonian forms are represented by very few individuals. The Miocene records a decline in the number of species, and since Miocene (Awamoan) beds are the most richly fossiliferous in New Zealand, and yield a large number of species and individuals, this is rather to be wondered at. It is

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more especially remarkable in contrast with the fossil Turbonillids, which attained their maximum importance at this time. Seven species are found in the Pliocene, but none of these have persisted from Miocene times, though five of them appear also in the Recent fauna. Four species are confined to the Recent.

Genus Odostomia Fleming.

1817. Fleming, Edinburgh, Encycl., vol. 7, pt. 1, p. 76.

Type (fide Dall and Bartsch): Turbo plicatus Montagu.

Odostomia in the strict sense has the following characters:— Spire not greatly elevated, few whorls, and a single columella-fold. The surface is typically smooth. Strong, universal spiral sculpture is absent. Fine microscopic spiral striae may, or may not, be present. Any spiral sculpture stronger than microscopic striae, if present, is confined to an incised line bordering the suture. The protoconch is low, considerably immersed, and thus contrasts with that of Turbonillids and Syrnolids. Cossmann (Ess. de Paléoconch. Comparée, p. 235, 1921) states that the protoconch is small and obtuse. His figure of the genotype shows (loc. cit., Planche-Texte A, fig. 81) the nucleus to be polygyrate and apparently helicoid.

Two groups based on the embryo can be distinguished. Group A of this paper comprises Odostomia with projecting lateral nucleus. Into Group B fall species whose lateral nucleus is not evident. Owing to the considerably immersed protoconch of Odostomia it has not been possible always to determine confidently the character of its coiling, for in cases where there is a little extra tilting or immersion the nucleus may be almost entirely hidden below the suture of the first normally coiled whorl.

Odostomia Group A.

Key To Species Of Odostomia A.

Whorls quite flat or nearly so.
 Periphery distinctly angled.
  Shell of moderate size, not less than 4.0 mm.
   Spiral sculpture entirely absent; suture indistinct, not at all cut in; outlines perfectly straight; growth-lines vertical obstinata
   Traces of indistinct spirals on last whorl; suture more cut in; outlines a little pupoid above vixornata
  Shell small, less than 4.0 mm.
   Shell heavy, stoutish; peripheral angulation not sharp; growth-lines oblique chattonensis
   Shell ol lighter build, not stout, but more elevated; peripheral angulation very well marked.
    Shell slender; whorls quite flat, overhanging suture. mahoenuica
    Shell not quite so slender; whorls lightly concave, swollen below suture and at periphery of last whorl. awatumida
 Periphery not distinctly angled.
  Shell 5 5 mm. high or over; outlines straight.
   Shell moderately tall and slender, suture margined below; periphery quite evenly rounded. waipaoa
   Shell not so slender, but body-whorl distinctly wider; suture not margined below, but an incised spiral line on periphery; periphery sub-angled. bartrumi
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 Shell considerably less than 5.5 mm. high; outlines pupoid.
  Spire gradate; periphery low, sub-angled; spirals lacking. ancisa
  Spire not gradate; periphery higher, not sub-angled. Suture margined on both sides by incised spiral lines. pervaga
   Suture not margined, shell minute. geoffreyi
Whorls convex, not flat.
 Shell 3.0 mm. tall or over.
 Whorls only lightly convex.
  Fine microscopic striae present.
   A single incised spiral line present bordering suture behind and on periphery of last whorl. Spiral cords absent.
    Shell large, of heavy build; whorls more bulging over lower third and much broader than high; body-whorl less than half height of shell. pudica
   Spiral cords present.
    Irregular, low spiral cords present; shell rather stout. chordata
  Two incised spiral lines present, one bordering each side of suture.
  Shell fairly large, of heavy build; outlines straight; columella almost straight. zecorpulenta
  Fine microscopic striae absent.
   Outlines straight to lightly convex; height of body-whorl less than half that of shell; embryo large and heavy; shell narrowly umbilicate. vaga
 Whorls strongly convex; sutures well impressed.
  Shell stout; body-whorl capacious, its height half that of shell; umbilicate; no spirals present. takapunaensis
Shell not stout; body-whorl less in height than half that of shell; not umbilicate; a single incised spiral line above suture. incidata
 Shell less than 3.0 mm. high.
  Spire gradate; sutures much, impressed.
   Whorls flatly convex; shell thick and heavy for its size; an incised spiral line above suture. sherriffi.
  Spire not gradate; suture not strongly impressed.
   Aperture rhomboidal; whorls a little overhanging; columella-fold inconspicuous. waitakiensis
   Aperture sub-ovate.
    Columella-fold pronounced giving a strong twist to columella and placed below insertion. ototarana
    Columella-fold small, not unduly pronounced, situated at insertion; two incised spirals, one bordering each side of suture. turneri

Note.—O. arowhana (Marwick) is not included in the key, as the unique holotype has been lost, and no specimen has been available for study.

Odostomia obstinata n.sp. (Fig. 11.)

Shell small, conic; spire elevated, about 2 ½ times height of aperture, its outlines straight. Post-nuclear whorls 6 ½ in number, quite flat, the sharply angulated periphery closely overhanging suture. Protoconch small, heterostrophic, coiled in a helicoid spiral of about two volutions, the nucleus rather less than one-half immersed.

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Axial sculpture absent; spiral sculpture represented by the peripheral angulation only. Body-whorl short, flat above, its periphery strongly angled and bearing a low spiral cord; base short, lightly convex, rapidly retreating to axis of shell; aperture quadrate, angled behind, broadly rounded in front, the outer lip somewhat effuse, especially below; columella thick, set vertically, arcuate, a moderately strong, horizontal plait near its insertion; inner lip with a thin, narrow band of callus; outer lip straight.

Height, 4.4 mm.; width, 2.0 mm. (holotype).

Localities: Shell-bed, Target Gully, Oamaru (type); Pukeuri, Oamaru; Rifle Butts, Oamaru; Ardgowan, near Oamaru; Chatton, near Gore; Clifden, Southland, new road-cutting behind racecourse (= band 7 of the beds along the river), also bands 6A, 8A. All are Awamoan horizons with the exception of band 6A, Clifden, which is Hutchinsonian; and Chatton (Ototaran).

Type in Auckland Museum (ex writer's collection).

Odostomia vixornata (Marwick). (Fig. 2.)

1931. Syrnola vixornata Marwick, N.Z. Geol. Surv. Pal. Bull., no. 13. p. 105, fig. 198.

This has not the long tapering habit of typical Syrnola, and is better located in Odostomia. The single specimen has its surface too poorly preserved to permit any definite pronouncement concerning the nature of its sculpture, though on the body-whorl there are indications of several widely spaced incised spiral lines. The pillar-plait looks very strong and probably influenced Dr. Marwick, but the aperture is broken. The protoconch, which is heterostrophic and of helicoid coiling, is depressed as in Odostomia and not exsert as in Syrnola. The flattened whorls and general habit are reminiscent of O. waipaoa (Marwick), also from Gisborne District.

Height, 4.8 mm.; width, 1.8 mm.

Locality: N.Z.G.S. loc. 1237, Gisborne District, Ihungia Series (Hutchinsonian).

Type (unique) in collection of N.Z. Geological Survey, Wellington.

O. bartrumi n.sp. is a similar shell, but has a blunter apex, less sharpened summit to spire, and possesses a single incised spiral line close above suture.

Odostomia chattonensis n.sp. (Fig. 20.)

Shell very small, conic, of heavy build; spire just over twice height of aperture, its outlines straight to faintly convex. Post-nuclear whorls 5 ½ in number, quite flat, and angled at periphery; suture only a little impressed. Protoconch heavy for size of shell, heterostrophic, coiled in a helicoid spiral of about two volutions, its nucleus large and one-half immersed. Axial sculpture absent; spiral sculpture of excessively fine microscopic striae. Body-whorl short, flat above, its periphery sub-angled; base short, lightly convex, rapidly drawn in to axis of shell; apertural features as for O. obstinata, but plait not so prominent; outer lip broken away.

Height, 3.0 mm.; width, 1.3 mm. (holotype).

Locality: Chatton, near Gore, Southland (Ototaran).

Type in Auckland Museum (ex writer's collection).

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This species differs from O. obstinata, its nearest ally, in its constantly smaller size, heavier embryo, and in its possession of spiral striae. Also, the growth-lines are antecurrent to posterior suture and not vertical as in obstinata.

Odostomia mahoenuica n.sp. (Fig. 15.)

This species is undoubtedly of the same lineage as O. obstinata, from which it is distinguished by its smaller size, more attenuate habit, and heavier and larger embryo with strongly bulging nucleus. The plait is rather weaker, and the whorls, which are quite flat, are more sharply angled above suture, which they overhang more than do those of obstinata.

Height, 3.0 mm.; width, 1.0 mm.

Locality: Mahoenui beds, Awakino River, about one mile east of north entrance to Awakino Gorge (Hutchinsonian);Blue Cliffs.

Type in writer's collection

Odostomia awatumida n.sp. (Fig. 13.)

This species also is a close relative of O. obstinata and its allies. It is distinguished by small size, light build, excessively fine microscopic striae (seen only on good specimens), light plait, and a low sub-sutural swelling frequently causing whorls to appear faintly concave. The suture is but little impressed. The margined suture separates awatumida from related species; the whorls are not overhanging, though the angulation is quite distinct.

Height, 2.7 mm.; width, 1.0 mm. (holotype).

Localities: White Rock River (type); Sutherlands, South Canterbury. Both are Awamoan horizons.

Type in Auckland Museum (ex writer's collection).

subsp. convexa nov.

Certain shells from White Rock River, Sutherlands, Holme Station, and Opihi River (all Awamoan horizons near Timaru, South Canterbury) have the spire lightly convex in outline, the subsutural swelling more pronounced, and the whorls somewhat staged. This form is not considered distinct enough from the species to warrant more than varietal separation from it.

Odostomia waipaoa (Marwick). (Fig. 9.)

1931. Syrnola waipaoa Marwick, N.Z. Geol. Surv. Pal. Bull., no. 13, p. 105, fig. 200.

1931. Syrnola lutosa Marwick, N.Z. Geol. Surv. Pal. Bull., no. 13, p. 106, figs. 194, 199.

This species is of high conic habit, but is not sufficiently slender for Syrnola, and is accordingly removed to Odostomia. The sunken heterostrophic protoconch is of helicoid coiling, the nucleus about one-half immersed, and Odostomid, not Syrnolid. Fine microscopic striae are not developed, but two incised spiral lines are present, one as a margin below posterior suture, the other just above anterior suture. This is typical of many other New Zealand Odostomia, and not of Syrnola.

Syrnola lutosa Marwick and the present species are undoubtedly conspecific, and lutosa must give place to waipaoa, which has page preference. Marwick, in comparing these two forms, distinguishes

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the former from waipaoa by its sub-angled periphery of body-whorl and by the absence of a bordering spiral thread below the suture. The type is the only specimen of lutosa, and, though the surface is finely corroded, there is one portion well enough preserved to show two incised spiral lines as in waipaoa. Further, as lutosa is hardly adult, the sub-angulation of the body-whorl is expectable, for in immature specimens of Odostomia the same character is frequently present, and it is usually only the fully adult shells that possess the regularly convex periphery of the body-whorl. Immature specimens of waipaoa have the same sub-angulation.

Height, 5.9 mm.; width, 2.0 mm. (holotype).

Locality: N.Z.G.S. loc. 1236, Gisborne District, Ihungia Series(Hutchinsonian).

Type and a number of paratypes in collection of N.Z. Geological Survey, Wellington.

Odostomia bartrumi n.sp. (Fig. 1.)

Shell of moderate size, elongate-conic; height of spire nearly twice that of body-whorl, its outlines straight. Post-nuclear whorls 6 ¾ in number, flat to very faintly convex; suture incised. Protoconch heterostrophic, of about two volutions, coiled in a low helicoid spiral; nucleus small, its lower edge tangent to suture of first adult whorl. Excessively fine microscopic spiral striae absent; there is one incised spiral line close above suture, and indication of one or two obsolete, raised spirals near summit of last whorl. Body-whorl of moderate height flat above, roundly sub-angled at periphery, base convex and full; aperture sub-ovate, angled behind, not widely rounded in front; columella thin, set vertically, arcuate, its plait conspicuous, horizontal and situated just below insertion; outer lip thin, straight.

Height, 5.1 mm.; width, 2.0 mm. (holotype).

Locality: Kaawa Creek beds (Waitotaran).

Type and many paratypes in writer's collection.

Separated from related forms by its high spire and flat outlines. This shell is listed and figured as Odostomia sp. by Bartrum and Powell in their paper on the Kaawa Creek mollusca (Trans N.Z. Inst., vol. 59, p. 161, pl. 28, fig. 32, 1928). Several fine specimens have recently been collected.

Named in honour of its discoverer, Professor J. A. Bartrum, of the University College, Auckland.

Odostomia ancisa (Marwick). (Fig. 19.)

1931. Syrnola ancisa Marwick, N.Z. Geol.Surv. Pal. Bull., no. 13, p. 106, fig. 196.

This species is not of sufficiently tall habit to warrant its location in Syrnola, and it is here regarded as an undoubted Odostomid. The spire has convex outlines. The surface of the shell is badly preserved, so that spiral ornamentation may have been present. The apex is a typical Odostomid sunken one, not exsert as in Syrnola.

Height, 3.2 mm.; width, 1.4 mm.

Locality: N.Z.G.S. loc. 1340, Gisborne District, Ihungia Series (Hutchinsonian).

Type (unique) in collection of N.Z. Geological Survey, Wellington.

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Odostomia pervaga n.sp. (Fig. 14.)

Shell very small, conic; height of spire about half that of shell, its outlines convex. Post-nuclear whorls 4 ½ in number, earlier ones lightly convex, later ones nearly fiat; suture impressed. Protoconch small, sharpened at summit; heterostrophic, coiled in a helicoid spiral; nucleus about one-third immersed. Spiral sculpture consists of two incised lines close to suture, one posterior to it and the other anterior. Length of body-whorl about half that of shell, its outline flat above, sharply convex at periphery, broadly convex on base, which is fairly long; aperture sub-ovate, angled behind, not widely rounded in front; columella set vertically, arcuate, its plait heavy, strongly entering aperture, and situated not far below parieto-columella junction, which is obtusely angled; outer lip partially broken back, but apparently straight.

Height, 2.8 mm.; width 1.2 mm, (holotype).

Localities: Takapuna Beach, Auckland, in shell sand (type);Oneroa, Waiheke Island; Orua Bay, Manukau Harbour; junction of Ruakokopatuna and Makara Streams, South Wairarapa (Pliocene).

Type in Auckland Museum (ex writer's collection).

The flat whorls, convex outline, and heavy plait set below insertion of columella make this species distinctive.

Odostomia geoffreyi n.sp.

Shell minute, height of spire rather less than that of body-whorl its outlines straight. Post-nuclear whorls nearly four in number, very lightly convex to flat; suture distinct. Protoconch heterostrophic, the lateral nucleus considerably immersed and not prominently projecting. Faint microscopic spiral striae present on most whorls; incised spiral lines absent. Body-whorl slightly over half height of shell, its periphery strongly convex; base flattish; aperture pyriform; columella arcuate, set vertically, a small but distinct plait at insertion.

Height, 1.85 mm.; width, 0.85 mm. (holotype).

Locality: Auckland Harbour (type); Onetangi, Waiheke Island.

Type in writer's collection.

This is the smallest of our Recent Odostomia. A figure of this species will be given in the next part of this series of papers.

Odostomia pudica Suter. (Fig. 3.)

1908. Odostomia pudica Suter, Trans. N.Z. Inst., vol. 40, p. 366, pl. 29, fig. 14.

1913. Odostomia pudica Suter, Man. N.Z. Moll., p. 340, pl. 17, fig. 1 (Atlas).

Suter's description of shape of whorl is hardly satisfactory. It cannot strictly be regarded as “flat,” for the lower half is somewhat swollen and more bulging than the zone above; it is drawn in moderately rapidly to anterior suture and cut in closely and horizontally to posterior one. A little posterior to suture and almost on the greatest bulge of whorl there is one incised spiral line, which is continued around periphery of last whorl, and this no doubt gave

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Suter the impression of an “angle” on the whorls, which, however, is not strictly correct. Fine microscopic striae can here and there be picked up. The type specimen is a beach shell, rather worn, and it is probable that the striae, originally universal, have been obliterated. The protoconch is heterostrophic, helicoid (low), and very considerably immersed, so that only an extremely narrow zone of nucleus appears.

Height, 5.2 mm.; width, 2.2 mm. (holotype).

Localities: Bay of Islands (type); Takapuna, Auckland.

Type in Wanganui Museum.

The type is the only undoubted specimen the writer has seen. Suter (Manual, p. 340) has compared his species with O. hyphala Watson, from 700 fathoms north-east of East Cape (Challenger Station 160). The type of Watson's species, however, is lodged in the British Museum, so that no comparison can be made by the present writer.*

Here again Suter's figure is at fault, quite useless, and entirely misleading. In his description the whorls are described as “flat”; but his illustration shows them very strongly convex with deeply cut in sutures, and is not at all reminiscent of the actual specimen.

Odostomia chordate Suter. (Fig. 10.)

1907. Odostomia (Evalea) chordata Suter, Trans. N.Z. Inst., vol. 40, p. 348, pl. 27, fig. 5.

1913. Odostomia (Evalea) chordata Suter, Man. N.Z. Moll., p. 342, pl. 17, fig. 5 (Atlas).

A glance at this shell is sufficient to raise one's doubts as to its correct location in Evalea. The sculpture of narrow cords separating the wider unsculptured areas is certainly not that of the group to which Suter referred the species. Two characters point unmistakably to its affinity with Odostomia. First, there is an incised spiral line forming a margin posterior to the suture, and this, as already seen, is a feature very common amongst certain Neozelanic species of Odostomia. Second, the embryo is a quite typical Odostomid one; the summit of the shell has not the Evalea “look,” and the lateral nucleus is apparent, a little over one-half immersed, and coiled in a low helicoid spiral.

The spiral cords are weak, irregularly spaced, and obsolete in parts, and it is doubtful whether additional material would show them to be a constant feature of the species.

Height, 3.6 mm.; width, 1.8 mm. (holotype).

Locality: Five miles south of Cuvier Island, in 38 fathoms; Hen and Chickens Islands, in 25 fathoms; Petane (Nukumaruan).

Type in Wanganui Museum.

[Footnote] * Watson's figure and description show that his species can be distinguished from pudica by absence of spiral lines, and by flexuous growth-lines, very slight plait, and shorter base. The outline of whorl is very similar in both species.

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Odostomia zecorpulenta n.sp. (Fig. 7.)

Shell rather large, narrowly umbilicate, conic, elevated; height of spire one and one-third times that of body-whorl, its outlines straight. Post-nuclear whorls 6 in number, faintly convex; suture well impressed. Protoconch small, tilted, coiled in a low helicoid spiral; nucleus about one-half immersed. Spiral sculpture of obscure microscopic striae, seen here and there on good specimens only; suture faintly margined below by an incised spiral line, and above by a much stronger incised spiral; several low, widely spaced, almost obsolete spirals traverse centre part of whorl. Body-whorl remarkably distended and strongly convex from suture down over base (in immature shells only is the periphery sub-angled); aperture very broadly ovate; columella set vertically, arcuate, its plait small and situated not far below insertion; parietal wall thinly callused; outer lip straight.

Height, 5.3 mm.; width, 2.2 mm. (holotype).

Localities: Petane, Hawke's Bay, Pliocene (Nukumaruan), type; junction of Ruakokopatuna and Makara Streams, South Wairarapa (Pliocene); Kereru and Devil's Elbow (Nukumaruan).

Type in writer's collection.

Odostomia vaga n.sp. (Fig. 18.)

Shell small, narrowly umbilicate, conic; spire moderately elevated, twice height of aperture, its outlines straight. Post-nuclear whorls 4 ¾ in number, convex; suture well impressed. Protoconch large, conspicuous, of heavy build, heterostrophic, coiled in a high helicoid spiral, the nuclear portion very strongly projecting, almost overhanging succeeding volution; nucleus small, practically free of immersion. Spiral sculpture absent. Height of body-whorl less than half that of shell; body-whorl convex above and on base, periphery angulated; aperture ovate, well opened out; columella set vertically, arcuate, a light but definite plait just below its insertion; inner lip callused; outer lip thin, straight.

Height, 3.6 mm.; width, 1.8 mm. (holotype).

Localities: Off Oamaru, in 50 fathoms (type);off Otago Heads, in 40 to 50 fathoms; Hen and Chickens Islands, in 25 fathoms; Snares Islands, in 50 fathoms; Petane, Hawke's Bay, Pliocene (Nukumaruan);Te Piki, Cape Runaway (Castlecliffian).

Type in Auckland Museum (ex Finlay collection).

The character of embryo, angulated periphery, and presence of umbilical perforation serve to distinguish this species, which must be a very hardy one, as shown by its extended Recent distribution and its range in time.

Odostomia takapunaensis Suter. (Fig. 5.)

1908. Odostomia takapunaensis Suter, Trans. N.Z. Inst., vol. 40, p. 365, pl. 28, fig. 10.

1913. Odostomia takapunaensis Suter, Man. N.Z. Moll., p. 341, pl. 17, fig. 2 (Atlas).

Suter's description of this species as “narrowly umbilicate” is not precise, at least so far as it relates to adult shells, for the type of his species and many topotypes are rather widely perforated for

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Odostomia, The shell is short and stout, and consists of about five post-nuclear whorls. The figure in the Atlas is of little use. It shows the whorls much too convex, and omits the sub-angulation at periphery of body-whorl, which itself is not shown sufficiently wide in relation to height. The protoconch is greatly submerged as a whole, and is in a low helicoid spiral, the small lateral nucleus about one-half emergent. There is no spiral sculpture.

Height, 3.65 mm.; width, 2.0 mm. (holotype).

Locality: Takapuna reef, Auckland, in sand (type); Oneroa, Waiheke.

Type in Wanganui Museum. A number of topotypes from Takapuna Beach and from 3—4 fathoms off Takapuna in writer's collection.

Odostomia incidata Suter. (Fig. 8.)

1908. Odostomia incidata Suter, Trans. N.Z. Inst., vol. 40, p. 348, pl. 27, fig. 6.

1913. Odostomia incidata Suter, Man. N.Z. Moll., p. 338, pl. 16, fig. 21 (Atlas).

This species is reminiscent of O. pudica Suter, which also is a tall form of somewhat similar build. Further similarity lies in the possession by both species of a single incised spiral line above sutures. Pudica, however, has a sub-angled periphery, which is absent in the present species. Suter's figure of incidata shows the whorls too convex. The protoconch is in a low helicoid spiral, the nucleus rather more than one-half immersed.

Suter's paratype is an encrusted shell, and doubtfully referable to this species.

Height, 4.3 mm.; width, 1.6 mm. (holotype).

Localities: Five miles south of Cuvier Island, in 38 fathoms (type); Hen and Chickens Islands, in 25 fathoms.

Type in Wanganui Museum.

The shells from Hen and Chickens Islands in particular are rather stouter than the type, but in other respects possess all the characters of the species. Possibly this divergence in habit is to be explained by abnormality in the growth of the holotype itself, for a serious fracture crosses one of the mid-spire whorls.

Odostomia sherriffi Hutton. (Fig. 17.)

1883. Odostomia sherriffi. Hutton, Trans. N.Z. Inst., vol. 15, p. 411.

1893. Odostomia sherriffi Hutton, Macleay Mem. Vol. Plioc. Moll., p. 58.

1900. Actaeon minutissima Murdoch, Trans. N.Z. Inst., vol. 32, p. 216, pl. 20, fig. 5.

1915. Odostomia (Jordaniella) sherriffi Hutton. Suter. N.Z. Geol. Surv. Pal. Bull., no. 3, p. 10, pl. 8, fig. 17.

Suter's reference to Jordaniella cannot be upheld. A very narrow, microscopic, incised spiral line traverses most whorls not far above suture. In no sense can this be regarded as a sulcus, so that the name Jordaniella must be dropped. Though incidata acutangula, and pudica are likewise characterised by the presence of a fine peripheral spiral groove, Suter did not locate them in Jordaniella. but in Odostomia s.str.

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The protoconch is heterostrophic, in a low helicoid spiral, the nucleus about one-half immersed.

Suter's drawing in the Palaeontological Bulletin gives a fair representation of the general form of the shell, but it makes his so-called “sulcus” much too prominent a feature. Striae are entirely absent.

Height, 2.4 mm.; width, 1.0 mm. (holotype).

Localities: Wanganui, Pliocene (type); Big King Island, in 100 fathoms; Petane (Nukumaruan).

Type in Canterbury Museum, Christchurch.

The topotypes have not so prominent a shoulder on the whorls; otherwise they match the type well. Some of the shells from Big King Island show faint indication of a subsutural incised spiral line.

Odostomia waitakiensis n.sp. (Fig. 4.)

Shell very small (probably not quite adult), conic, of heavy build for its size; height of spire 1 ½ times that of aperture, its outlines straight. Post-nuclear volutions 3 ¾ in number, very lightly convex, sub-angled at periphery and a little overhanging; suture not very distinct. Protoconch heavy, heterostrophic, coiled in a helicoid spiral, its nucleus large and very little immersed. Spiral sculpture absent. Body-whorl half height of shell, very lightly convex to flattish above, periphery sub-angled; base fairly long and lightly convex; aperture quadrate, angled behind, fairly widely rounded in front; columella thick, set vertically, a little arcuate, the plait indicated by a light swelling at its insertion; outer lip straight.

Height, 1.8 mm.; width, 0.9 mm. (holotype).

Locality: Otiake (Waitakian).

Type in Auckland Museum (ex Finlay collection).

The light convexity of whorl, long body-whorl, and lack of spiral sculpture separate this species from O. chattonensis. From O. obstinata it is distinguished by smaller size, heavier build, convexity of whorl, and long body. The lightly convex whorl also separates it from mahoenuica.

Odostomia ototarana n.sp. (Fig. 6).

Shell very small, conic; height of spire a little less than that of body-whorl, its outlines straight. Post-nuclear whorls 3 in number, lightly convex; suture impressed. Protoconch large and heavy for size of shell, heterostrophic, coiled in a high helicoid spiral; nucleus markedly projecting and overhanging first adult volution. Spiral sculpture of excessively fine microscopic striae (seen on paratype). Height of body-whorl greater than half that of shell; body-whorl flatly convex above, convex to sub-angled at periphery, base flattish, slightly concave towards columella; aperture sub-ovate, angled behind, not widely rounded in front; columella set vertically, arcuate, with a strong twisted fold spirally entering aperture; inner lip not callused; outer lip thin, straight.

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Height, 1.7 mm.; width, 0.9 mm. (holotype).

Locality: Chatton, near Gore, Southland (Ototaran).

Type in writer's collection.

The heavy embryo of high helicoid coiling and strong twisted plait are characteristic.

Odostomia turneri n.sp. (Fig. 16.)

Shell very small, conic; height of spire 1 ½ times that of aperture, its outlines straight. Post-nuclear whorls 4 in number, lightly convex; suture not much impressed. Protoconch heterostrophic, coiled in a low helicoid spiral, nucleus considerably immersed. Fine microscopic spiral striae absent; spiral sculpture represented by two incised lines, one margining posterior suture, the other close above anterior suture and on periphery of whorl. Height of body-whorl slightly over half that of shell, its outlines convex over periphery and base, flattish above; aperture sub-ovate, widely rounded in front, angled behind; columella thick, set vertically, arcuate, its plait horizontal and situated near insertion; inner lip shows no callus; outer lip thin, straight.

Height, 2.5 mm.; width, 1.2 mm. (holotype).

Locality: Castlecliff, Wanganui (Castlecliffian), type; Manukau Harbour (Recent); Devil's Elbow, Napier—Wairoa Road (Nukumaruan); Kaawa Creek (Waitotaran); Hawera (Waitotaran).

Type in Auckland Museum (ex writer's collection).

Named in honour of Dr. F. J. Turner, Department of Geology, Otago University.

Incertae sedis.

Odostomia, arowhana (Marwick). (Fig. 12.)

1931. Syrnola, arowhana Marwick, N.Z. Geol. Surv. Pal. Bull., no. 13, p. 106, fig. 197.

The unique holotype has been lost, so that it has not been possible to examine the embryonic characters of this species. In the meantime, then, until further specimens are available, the species is not definitely located. According to Marwick the sculpture is similar to that of O vixornata, which is located in Odostomia Group A, but if the apex proves to be of planispiral type, it will have to be referred to Odostomia Group B.

Arowhana is not sufficiently attenuate for Syrnola, where Marwick originally placed it.

Height, 4.5 mm.; width, 1.8 mm.

Locality: Tutamoe Series, N.Z.G.S. loc. 1298 (Awamoan), Gisborne District.

The illustration is a reproduction of Dr. Marwick's figure.

Odostomia Group B.

Group B has all the characters of Group A save that the nucleus is not evident projecting laterally. In species in which the protoconch is not greatly depressed it is seen to be paucispiral and planorboid; but in others the considerably sunken embryo makes it impossible to observe the lateral nucleus, so that the character of embryonic

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coiling cannot be definitely established; for, as pointed out earlier in this paper, where there is a little extra tilting or immersion of the embryo, the nucleus may become entirely bidden below the suture-of the first normally coiled whorl.

Key TO Species OF Odostomia B.

Shell 3.5 mm. in height or over.
 Whorls flat or nearly so, overhanging suture, angulated; plait small but distinct.
  Periphery distinctly angled; outlines straight; whorls quite flat castlecliffensia.
  Periphery sub-angled; outline rather pupoid towards summit; whorls very lightly convex; peripheral thread present. haurakiensis
 Whorls convex, not flat; plait not distinct.
  Whorls strongly convex, roundly shouldered, spire gradate murdochi
  Whorls not strongly convex, little or not shouldered; spire not gradate.
   Height of aperture less than one-third that of shell.
    Whorls moderately convex, little shouldered; no spiral sculpture whatever; protoconch considerably exsert. vestalis
    Height of aperture greater than one-third that of shell.
    Whorls lightly convex; not shouldered.
     Microscopic striae present; one incised spiral line below suture pedica
     Microscopic striae absent; two incised spiral lines bordering each side of suture. aucklandica
Shell less than 3.5 mm. high.
 Microscopic spiral striae present.
  Incised spiral sculpture absent.
   Columella with a strong twisted plait; whorls very flatly convex; suture not much impressed; periphery sub-angled. gorensis
   Columella-fold weak or almost obsolete.
    Suture moderately impressed.
    Height of aperture nearly one-third that of shell, which is well elevated.
     Body-whorl high; no angulation; aperture narrowly ovate. cryptodon
     Body-whorl wide, sub-angled at periphery; aperture broadly and roundly ovate.
      Peripheral cord present. acutangula
      Peripheral cord absent. parvacutangular
     Height of aperture nearly half that of shell, which is distinctly squat. taumakiensis
    Suture strongly impressed; whorls flatly rounded; body-whorl angulated at periphery, with a weaker angulation just below. biangulata
   Incised spiral sculpture present.
    Two incised spiral lines bordering each side of suture; shell not stout; whorls flatly convex; protoconch not depressed but erect. manukauensis.
  Microscopic spiral striae absent.
   Incised spiral sculpture absent; shell very small with a strong twisted plait and heavy embryo. graviapicalis
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Odostomia castlecliffensis n.sp. (Fig. 21.)

Shell of moderate size, high conic; height of spire 2 ½ times that of aperture, outlines straight. Post-nuclear whorls 5 ¾ in number, flat, the periphery, which is low down near suture, distinctly angled and bearing a low spiral thread; suture strongly incised. Protoconch heterostrophic, planispiral; nucleus almost wholly immersed. Spiral sculpture confined to the weak thread on periphery. Body-whorl in height a little less than half that of entire shell, flat above, strongly angled on periphery, convex on base; aperture rhomboidal; columella set vertically, arcuate, its plait very weak and inconspicuous and situated at insertion. There is the very slightest indication of a narrow, almost linear umbilical chink; inner lip narrowly callused; outer lip straight, but angulated at periphery of whorl.

Height, 4.1 mm.; width, 2.0 mm. (holotype).

Locality: Castlecliff, Wanganui (Castlecliffian).

Type in Auckland Museum (ex writer's collection).

This species simulates O. obstinata, common in Awamoan beds at North Otago localities, but the divergent apical characters provide a ready means of separation.

Odostomia haurakiensis n.sp. (Fig. 24.)

Shell small, narrowly umbilicate, high conic; height of spire 2 ½ times that of aperture, outlines pupoid. Post-nuclear whorls 5 ½ in number, convex, overhanging; the low periphery distinctly angled; suture deeply incised. Protoconch heterostrophic, planispiral, low; nucleus almost completely immersed. Spiral sculpture confined to a fine thread on angulated periphery. Body-whorl in height a little less than half that of shell, flatly convex above and on base, sub-angled at periphery; aperture broken, but probably originally rhomboidal; columella set vertically, arcuate, its plait moderately conspicuous and situated almost at insertion; inner lip narrowly callused; outer lip broken.

Height, 3.9 mm.; width, 1.7 mm. (holotype).

Locality: Hauraki Gulf, in 28 fathoms.

Type(unique) in Auckland Museum (ex Finlay collection).

The present species is a very close relative of O. castlecliffensis, and they both possess the same general style of shell. A ready means of separation is to be had, however, in the rather pupoid outline, heavier plait, more open umbilicus and more convex whorl of haurakiensis.

Odostomia murdochi Suter. (Fig. 32.)

1904. Odostomia proxima Murdoch, Trans. N.Z. Inst., vol. 37, p. 226, pl. 8, fig. 19; not of de Folin, 1872.

1913. Odostomia murdochi Suter, Man. N.Z. Moll., p. 340, pl. fig. fig. 24 (Atlas).

The type material of this species consists of four shells, no particular one of which was designated as holotype by either Murdoch or Suter. None of the specimens agrees exactly with the dimensions given by Murdoch and copied by Suter, so that the writer now selects as lectotype the shell which most nearly approaches the

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recorded dimensions. Suter's figure in the Atlas is a reproduction of Murdoch's drawing, and does not do justice to any one of the four shells. It makes the habit rather less stout than is typical, and does not portray the true shape of whorl. The outline of whorl is not evenly convex, as shown in Murdoch's illustration, but is flatly convex over centre and drawn in rather rapidly to sutures, especially to the posterior one, where there is almost a tabulation, so that the spire appears somewhat staged.

The protoconch is heterostrophic, apparently planispiral, the nucleus almost completely hidden in succeeding whorl.

Height, 4.0 mm.; width, 1.8 mm. (lectotype).

Localities: Whangaroa Harbour (type); Banks Peninsula, recorded by Iredale, fide Suter, Manual; but in the light of other distributions shown by the present paper this may be questioned.

Type in Dominion Museum, Wellington.

Odostomia vestalis Murdoch. (Fig. 33.)

1905. Odostomia vestalis Murdoch, Trans. N.Z. Inst., vol. 37, p. 227, pl. 8, fig. 20.

1913. Odostomia vestalis Murdoch. Suter, Man. N.Z. Moll., p. 342, pl. 17, fig. 4 (Atlas).

The figure in the Atlas shows the whorls too flat and not sufficiently shouldered. The protoconch is more exsert than is usual for Odostomia, and is large, rather globose and planispiral. The general build and features of body-whorl and aperture remind one of Gumina, but the spire is much too high and the apex different.

Height, 4.4 mm.; width, 1.5 mm. (holotype).

Locality: Whangaroa Harbour.

Type in Dominion Museum, Wellington.

Odostomia pedica n.sp. (Fig. 34.)

Shell small, high conic; height of spire about 1 ½ times that of aperture, outlines straight. Post-nuclear whorls 4 ½ in number, convex; suture impressed. Protoconch heterostrophic, planispiral; nucleus about one-half immersed. Fine microscopic striae present here and there on all whorls; one incised spiral line margins suture below. Body-whorl in height slightly over half that of shell, broadly convex in one sweep from suture to base; aperture subovate, angled behind, fairly widely rounded in front; columella set vertically, arcuate, its plait not visible externally, but seen as a low fold within aperture; inner lip narrowly callused; outer lip thin, straight.

Height, 3.8 mm.; width, 1.6 mm.

Locality: Snares Islands.

Type (unique) in Wanganui Museum.

This species has been separated from among Suter's paratypes of O. inornata, which has an apex of helicoid type, and from which it is also distinct in having the suture margined.

Odostomia aucklandica n.sp. (Fig. 28.)

Shell of moderate size, conic, moderately elevated; height of spire twice that of aperture, outlines straight. Post-nuclear whorls

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4 ½ in number, convex, closely shouldered above; suture well impressed. Protoconch heterostrophic, apparently planispiral, low; nucleus almost completely immersed. Pine microscopic spirals present; two fine incised spiral lines present bordering both anterior and posterior sutures; spiral sculpture seen only on good specimens. Body-whorl in height a little greater than half height of shell, its outline convex throughout in one broad sweep from suture to base; aperture broadly ovate, angled behind, effuse in front; columella about vertical, arcuate, its fold exceedingly weak, almost obsolete; inner lip distinctly narrowly callused; outer lip thin, straight.

Height, 4.1 mm.; width, 1.95 mm. (holotype).

Locality: Faith Harbour, Auckland Islands.

Type in Auckland Museum (ex Finlay collection).

O. aucklandica combines the characters of both O. cryptodon and O. murdochi. It resembles the former in possession of a weak plait and in apertural shape, and the latter it simulates very closely in general build of whorl and character of suture. The Faith Harbour shells, however, show some variability in the depth of incision of suture, and not all have the suture so deeply impressed and the shoulder so strong as murdochi. Cryptodon is a much smaller species-with suture less incised and the body-whorl higher, and it lacks, incised spiral lines.

Odostomia gorensis n.sp. (Fig. 26.)

Shell very small, conic; height of spire 1 ½ times that of aperture, its outlines straight. Post-nuclear whorls 3 ¾ in number, very lightly convex; suture not strongly impressed. Protoconch large for size of shell, rounded over summit, planorboid. Sculpture consists of excessively fine, rather wavy, microscopic spiral striae. Body-whorl in height equal to half that of shell, flatly convex above, sub-angled at periphery, convex on base; aperture rhomboidal, angled behind, moderately widely rounded in front; columella thick, a little oblique, arcuate, its plait conspicuous, blunt and situated some distance below insertion; inner lip not callused; outer lip straight.

Height, 2.2 mm.; width, 1.1 mm.

Locality: Chatton, near Gore, Southland (Ototaran).

Type (unique) in writer's collection.

Odostomia, cryptodon Suter. (Fig. 29.)

1908. Odostomia cryptodon Suter, Trans. N.Z. Inst., vol. 40, p. 365, pl. 29, fig 12.

1913. Odostomia. cryptodon Suter, Man. N.Z. Moll., p. 335, pl. 16, fig. 16 (Atlas).

Suter gives a very fair illustration of this species, but he shows the pillar insufficiently excavated and the body-whorl contracted to base too low down and too sharply. The planispiral apex is considerably immersed.

Height, 2.7 mm.; width, 1.5 mm. (holotype). Corresponding dimensions of shell from Dunedin Harbour: 4.0 mm.; 1.9 mm.

Localities: Te Onepoto Bay, near Lyttelton (type); Dunedin Harbour, under stones between tide marks; Moeraki; Taieri Beach; Chatham Islands (a worn shell); off Otago Heads, in 40 fathoms.

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Fig. 1. Odostomia bartrumi n.sp.; paratype, × 13. Fig. 2.—Odostomia inornata (Marwick); holotype, × 13. Fig. 3.—Odostomia pudica suter; holotype × 13. Fig. 4.—Odostomia wantakiensis n.sp.; holotype, × 13. Fig. 5—Odostomia takapunaensis suter; holotye, × 13. Fig. 6.—Odostomia ototarana n.sp.; holotype, × 13. Fig. 7.—Odostomia zecorpulenta n.sp.; holotype. × 13. Fig. 8.—Odostomia incidata Suter; holotype, × 13. Fig. 9.—Odostomia waipaoa (Marwick); holotype, × 13.

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Fig. 10.—Odostomia chordata Suter; holotype, × 13. Fig. 11.—Odostomia obstinate n.sp.; holotype. × 13. Fig. 12.—Odostomia arowhana (Marwick); holotype, × 13. Fig. 13—Odostomia acatnmida n.sp; holotype, × 13. Fig. 14.—Odostomia pervaga n.sp.; holotype. × 13. Fig. 15.—Odostomia mahoenuica n.sp; holotype, × 13. Fig. 16.—odostomia twneri n.sp.; holotype × 13. Fig. 17.—Odostomia sherriffi Hutton; holotype, × 13 Fig. 18.—Odostomia vaga n.sp.; holotyupe, × 13. Fig 19.—Odostomia ancisa (Marwick); holotype, × 13. Fig. 20.—Odostomia chattonesis n.sp.; holotype × 13.

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Fig. 21. Odostomia castlecliffensis n.sp.; holotype, × 13. Fig. 22.—Odostomia grariapicalis n.sp.; holotype, × 13. Fig. 23.—Odostomia biangulata n.sp.; holotype × 13. Fig. 24.—Odostomia haurakiensis n.sp; holotype, × 13. Fig. 25—Odostomia paracutangula n.sp; holotyope, × 13. Fig. 26.—Odostomia gorensis n.sp.; holotype × 13. Fig. 27.—Odostomia taumakiensis Suter; holotype × 13. Fig. 28.—Odostomia aucklandica n.sp.; holotype × 13. Fig. 29.—Odostomia cryptodon Suter; holotype × 13. Fig. 30—Odostomia manukauensis n.sp; holotype, × 13. Fig. 31.—Odostomia acutangula Suter; holotype, × 13 Fig. 32.—Odostomia murdochi Suter; holotype × 13 Fig. 33.—Odostomia vestalis Murdoch; holotype × 13 Fig. 34—Odostomia pedica n.sp.; holotype × 13.

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Type in Wanganui Museum.

The Dunedin Harbour shells provide a very perfect match of the type, which is an immature specimen, the surface of which is not well preserved, so that Suter was led to record the absence of spiral sculpture for this species. The shells from Dunedin Harbour, however, have irregularly spaced, wavy microscopic striae.

Odostomia acutangula Suter. (Fig. 31.)

1908. Odostomia acutangula Suter, Trans. N.Z. Inst., vol. 40, p. 368, pl. 29, fig. 13.

1913. Odostomia acutangula Suter, Man. N.Z. Moll., p. 334, pl. 16, fig. 14 (Atlas).

Acutangula is known from a single specimen. The periphery is angled and the angulation carries a low spiral cord. The figure in the Atlas gives a fair representation of the whorls of the spire, but it shows the body-whorl hardly enough distended, the angulation too sharp, the columella straight instead of arcuate, and the aperture too narrow and not broadly enough rounded in front.

The protoconch is heterostrophic and apparently planorboid, of about one volution, and well tilted. Most of the nucleus is submerged.

Height, 2.4 mm.; width, 1.2 mm.

Locality: Port Pegasus, Stewart Island, in 18 fathoms.

Type in Wanganui Museum.

Odostomia parvacutangula n.sp. (Fig. 25.)

Shell very small, conic, moderately elevated; height of spire 1 ½ times that of aperture, outlines straight. Post-nuclear whorls 3 ¾ in number, lightly and evenly convex; suture impressed. Protoconch heterostrophic, planispiral, large, bulbous, exsert; nucleus about two-thirds immersed. Spiral sculpture not definite, traces of fine microscopic striae here and there. Body-whorl in height equal to about half that of shell, lightly convex above, flattish on base, periphery roundly angulated; aperture broadly oval, angled behind, effuse in front; columella thin, set vertically, arcuate, plait practically absent and indicated only by a broad, low swelling at insertion; inner lip thinly and narrowly callused; outer lip thin, straight; basal lip very broadly convex.

Height, 2.0 mm.; width, 1.0 mm (holotype).

Locality: Auckland Islands, in 95 fathoms.

Type in Auckland Museum (ex Finlay collection).

These Auckland Island shells are in build, shell-form, and apical characters very close to acutangula, from Stewart Island, but they are smaller and have less convex whorls and almost obsolete pillar-plait.

Odostomia taumakiensis Suter. (Fig. 27.)

1908. Odostomia taumakiensis Suter, Trans. N.Z. Inst., vol. 40, p. 363, pl. 28, fig. 7.

1913. Odostomia taumakiensis Suter, Man. N.Z. Moll., p. 341, pl. 17, fig. 3 (Atlas).

Suter's figure in the Atlas shows the whorls too convex; they should be moderately and evenly rounded. His comparison with O. murdochi is faulty in part. The salient separative features he

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does not comment on, viz., larger size and stouter habit of murdochi, which also has sutures much more strongly cut in and the spire somewhat stepped. The type of murdochi is imperforate, so that his comparison in reference to this character is of little value.

The protoconch is considerably immersed.

Height, 3.0 mm.; width, 1.5 mm. (holotype).

Localities: Taumaki Island, west coast of South Island, in 10 fathoms (type); Petane (Nukumaruan).

Type in Wanganui Museum.

Odostomia biangulata n.sp. (Fig. 23.)

Shell very small, conic; height of spire a little over twice that of aperture, outlines straight. Post-nuclear whorls 3 ½ in number, lightly convex, shouldered above, cut in rapidly close to suture below; suture strongly incised. Protoconch heterostrophic, apparently planispiral, large, bulbous; nucleus considerably immersed (partly broken). Fine, microscopic striae over whole surface of last whorl and on base; a spiral angulation on periphery of body-whorl, and another, not so strong, on base not far below peripheral one. Body-whorl in height about equal to half that of shell, shouldered at summit, flatly convex above the sub-angled periphery, convex on base; aperture sub-ovate, angled behind, rather effuse in front; columella about vertical, arcuate, its plait small, high up and seen only within aperture; inner lip as a narrow callus; outer lip straight.

Height, 2.0 mm.; width, 0.9 mm. (holotype).

Locality: Shell-bed, Target Gully, Oamaru (Awamoan).

Type in Auckland Museum (ex writer's collection).

The biangulate character of the last whorl is a good means of separation.

Odostomia manukauensis n.sp. (Fig. 30.)

Shell small, conic; height of spire 1 ½ times that of aperture, outlines straight. Post-nuclear whorls 4 ¼ in number, increasing rather rapidly in size, very lightly convex; suture distinct. Protoconch heterostrophic, low, rounded, apparently planispiral; nucleus almost completely immersed. Ill-defined microscopic spirals over surface of later whorls; in addition there are two strongly incised spiral lines situated respectively close to anterior and posterior margins of whorl. Body-whorl capacious, lightly convex above and on base, somewhat sharply convex at periphery; aperture broadly subovate; columella set vertically, arcuate, a small, low swelling near its insertion; inner lip thinly and narrowly callused; outer lip effuse, thin, straight; basal lip drawn down and inwards towards axis of shell.

Height 2.3 mm.; width, 1.3 mm. (holotype).

Locality: Orua Bay, Manukau Harbour (specimens from the collection of the Rev. W. H. Webster).

Type and several paratypes in War Memorial Museum, Auckland.

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Odostomia graviapicalis n.sp. (Fig. 22.)

Shell very small, conic; height of spire nearly twice that of aperture, its outlines straight. Post-nuclear whorls 4 in number, lightly convex; suture moderately impressed. Protoconch large, rather bulbous, planispiral; nucleus large, not central, a little immersed. Spiral sculpture entirely absent. Body-whorl in height equal to half that of shell, flatly convex above, sub-angled at periphery, flattish on base; aperture narrowly rhomboidal, acutely angled behind, produced downwards and inwards in front; columella a little oblique, arcuate, its plait distinct and a little below insertion; inner lip narrowly callused; outer lip straight.

Height, 2 1 mm.; width, 0.95 mm. (holotype).

Locality: Clifden, Southland, band 6A (Hutchinsonian).

Type in Auckland Museum (ex writer's collection).

Easily distinguished from gorensis by its lack of spiral sculpture, less stumpy habit, rather differently shaped aperture, and less marked angulation of body-whorl.