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Genus Syrnola A. Adams.
1860. Ann. Mag. Nat. Hist. (3) 5, p. 405. Type (by monotypy): Syrnola gracillima A. Adams.
Syrnola is reserved for slender, considerably elevated shells with a single more or less strong columella-fold and a heterostrophic embryo of helicoid coiling, whose nucleus is small, lateral and central. The Syrnolid apex is always exsert, and in this respect it resembles Turbonillid apices and differs from the depressed form of apex typical of Odostomia and related groups. Axial sculpture other than growth-striae is always lacking. There is no strong spiral ornamentation, but microscopic striae may, or may not, be present.
| Shell 5.0 mm. high or over. | |
| Shell moderately attenuate. | |
| Suture strongly impressed. | |
| Outlines straight; whorl-height between sutures low; whorls flattish; body-whorl short, inflated; protoconch broadly convex over summit. | wallacei. |
| Outlines convex; whorl-height between sutures much greater; whorls convex; body-whorl rather long, not inflated; protoconch sharper at summit | irrevocata. |
| Suture not strongly impressed, indistinct. | |
| Whorls flat; spire well sharpened; shell solid; apex very exsert. | aclyformis. |
| Whorls lightly convex; spire not so much sharpened; shell of lighter build; apex not unduly exsert; body-whorl more convex. | crawfordi. |
| Shell very attenuate. | |
| Whorls flat, a little overhanging; outline very elongately pupoid; plait very strong. | menda. |
| Shell considerably less than 5.0 mm. high. | |
| Outline practically straight; suture strongly incised; whorls flat; plait very distinct, thin and sharply elevated; body-whorl not angulated. | sculptilis. |
| Outline lightly convex; suture weak; whorls concave; periphery rather swollen and sub-angled; plait small and not so obvious. | sulcifera. |
Syrnola wallacei Marwick (Fig. 13).
1929. Syrnola wallacei Marwick, Trans. N.Z. Inst., vol. 59, p. 919, fig. 54.
In addition to the spiral threads on the periphery (referred to by Marwick in his description of the species), there are several very weak, sub-obsolete ones higher up on the whorl; one not far below suture, another at about the centre of whorl; and a third close above periphery. These can be picked up by orienting the shell almost parallel with the direction of travel of the light-rays, base towards the source of light. Fine microscopic striae are present between sutures and on the base of the shell.
Height, 4.75 mm.; width, 1.4 mm. (holotype).
Locality: Chatton, near Gore, Southland (Ototaran).
Type in collection of N.Z. Geological Survey, Wellington.
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Syrnola irrevocata n.sp. (Fig. 1).
Shell of moderate size, well elevated, outlines convex, summit sharp. Post-nuclear whorls nearly 7, convex; suture strongly impressed. Protoconch heterostrophic, of about 2 ½ volutions; lateral nucleus small, central. Growth-striae constitute the only sculpture. Body-whorl high, convex throughout; aperture broken, probably sub-rhomboidal; columella thick, set vertically, arcuate, its plait distinct, situated high up near insertion; inner lip lightly callused within aperture; basal and outer lips broken.
Height, 5.0 mm.; width, 1.5 mm. (holotype).
Locality: Petane, Hawke's Bay (Nukumaruan).
Type in collection of Dr. H. J. Finlay.
The convex, sharpened summit is reminiscent of S. menda, but the shell is much less attenuate, and has the body-whorl longer and the sutures a good deal more cut in.
Syrnola aclyformis Marwick (Fig. 4).
1929. Syrnola aclyformis Marwick, Trans. N.Z. Inst., vol. 59, p. 920, fig. 55.
Aclyformis has the small lateral nucleus entirely free of succeeding whorl, whereas in wallacei the nucleus is approximately one-half immersed. Microscopic striae are present between sutures and on base, poorly visible here and there on the holotype, but well preserved on some topotypes and on a specimen from Waikaia.
Height, 5.1 mm.; width, 1.4 mm. (holotype).
Localities: Chatton, near Gore, Southland; Waikaia. Both Ototaran.
Type in collection of N.Z. Geological Survey, Wellington.
Syrnola crawfordi Powell (Fig. 2).
1927. Syrnola crawfordi Powell, Trans. N.Z. Inst., vol. 58, p. 297, pl. 34, fig. 2.
S. crawfordi has straight outline, lightly convex whorls, and apex well rounded over summit. The whorls are not high between sutures and the body-whorl is rather expanded. Fine microscopic striae are present. The slightly arcuate pillar carries a small plait high up near insertion. There is a slight umbilical chink present.
Height, 5.25 mm.; width, 1.45 mm. (holotype).
Locality: off Ahipara, in 23 fathoms.
Type in collection of Mr. A. W. B. Powell, Auckland.
Syrnola menda Finlay (Fig. 6).
1913. Pyramidella (Syrnola) pulchra Brazier. Suter, Man. N.Z. Moll., p. 331, pl. 16, fig. 11 (Atlas).
1926. Syrnola menda Finlay, Trans. N.Z. Inst., vol. 57, p. 405, figs. 50, 51.
The embryo is coiled in a very low helicoid spiral, and the lateral nucleus is small and central.
Height, 6.7 mm.; width, 1.3 mm. (holotype).
Localities: near Cuvier Island, in 40 fathoms (type); Hen and Chickens Islands, in 25 fathoms; Poor Knights, in 60 fathoms.
Type in collection of Dr. H. J. Finlay.
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Syrnola sculptilis n.sp. (Fig. 3).
Shell very small, attenuated, outlines straight. Post-nuclear whorls 6 in number, perfectly flat, sharply cut in to suture both above and below. Protoconch heterostrophic, large, conspicuous, very much exsert, erect; low helicoid, central nucleus with its lower edge tangent to suture of first adult whorl. Except for growth-striae the shell is devoid of sculpture. Body-whorl flat above, periphery strongly convex, base lightly convex; aperture sub-rhomboidal (outer lip considerably broken away); columella broken in front, arcuate, its plait strong and situated high up; parieto-columellar junction obtusely sub-angled; basal and outer lips broken off.
Height, 2.8 mm.; width, 0.85 mm. (holotype).
Localities: Ardgowan shell-bed, Oamaru (type); Target Gully shell-bed, Oamaru; Clifden, Southland, band 8A. All are Awamoan horizons.
Type in Auckland Museum (ex writer's collection).
Syrnola sulcifera n.sp. (Fig. 9).
Shell very small, attenuate, spire sometimes a little stepped, outlines convex. Post-nuclear whorls 6 ½ in number, broadly and shallowly sulcate at centre; suture but little impressed. Protoconch heterostrophic, coiled in a low helicoid spiral, the lateral nucleus small, central, only very slightly immersed. Sculpture limited to growth-striae. Body-whorl concave above, angulated at periphery, convex on base; aperture sub-rhomboidal, angled behind, broad in front; columella vertical, arcuate, its plait small but distinct and situated a little below insertion; basal lip broadly rounded; outer lip straight.
Height, 2.3 mm.; width, 0.7 mm. (holotype). Corresponding dimensions of a paratype: 2.7 mm.; 0.8 mm.
Locality: Clifden, Southland, band 6A, and new road cutting behind racecourse = band 7C of the beds on right side along the river (type).
Type in Auckland Museum (ex writer's collection).