Plectostoma palinhelix (van Benthem Jutting, 1952)
Diagnostic description:
Shares with Plectostoma retrovertens the spire and tuba form, but differs by having spire height between 1.6–1.9 mm.
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Plectostoma palinhelix (van Benthem Jutting, 1952)
Plectostoma palinhelix (van Benthem Jutting, 1952)
General description:to be added
Conservation status:to be added
Diagnostic description:to be added
Taxon biology:See discussion under Plectostoma retrovertens.
Distribution:Bukit Serdam, Raub, Pahang, Malaysia.
Plectostoma palinhelix (van Benthem Jutting, 1952)
General description:Apex. Shape: slightly convex.
Spire. Height: 1.6–1.9 mm. Width: 1.1–1.3 mm. Number of whorls: 3 3/4–4 1/4. Apical spire shape: depressed conical. Basal spire shape: ovoid. Whorl periphery: moderately to distinctly convex. Umbilicus: partially or completely closed by tuba.
Constriction. Parietal teeth: two. Basal teeth: none.
Tuba. Coiling direction: type 2 and aperture visible between right lateral and back view; the tuba coils upward until the first teleconch whorl of the spire. Tuba whorl length similar to that of the last whorl of the spire. Proportion of tuba that attaches to spire: whole.
Aperture and peristome. Peristome: double peristomes. Outer peristome shape: similer to inner peristome, projected all around, except the posterior part, where the two lateral sides are slightly more projected than the anterior side.
Spiral lines. Thick lines: present. Thin lines: present.
Radial ribs. Rib density: 7–8 ribs per mm. Rib intensity: thin. Shape: straight. Inclination: orthoclin.
Conservation status:Vulnerable (B2ab(iii) ver. 10.1). There are four limestone hills in this area, of which Bukit Serdam and its next unnamed hill support populations (assessment done in 2010 and 2011). Two of the hills, namely, Bukit Serdam and Gunung Panas, are now being quarried. The smallest unnamed hill is highly degraded and Gua Kechil is surrounded by oil palm plantation.
Diagnostic description:Holotype: ZMA 136030(1) (Seen). Paratype: ZMA 136031(>10) (Seen).
Distribution:Type locality. Bukit Serdam, Pahang (3°49'47"N, 101°55'36"E).
Distribution range. To date, this species has been recorded from three limestone hills, namely Bukit Serdam, Gua Kechil and a small hill nearby (Figure 18C).
Plectostoma palinhelix (van Benthem Jutting, 1952)
Diagnostic description:BOR 466(1), BOR 5520(5), V 5104(5).
Plectostoma palinhelix (van Benthem Jutting, 1952)
Morphology:By van Benthem Jutting (1952)
"shell cylindrical-conical, yellowish to light-brown. First whorl smooth, subsequent ones ornamented with distantly placed fine ribs. These ribs are white or of the same colour as the rest of the shell, standing out wing-like away from the shell. Between the ribs there is a fine spiral sculpture. Shell not shining or transparent. Whorls 6, convex. The first two placed obliquely on the rest of the shell. These first whorls are lying almost in one plane, so that the top of the shell is very obtuse. the following whorls, especially the nos. 5 and 6 are bout equally broad. Hence the profile of this part of the shell is nearly cylindrical. last whorl irregular, constricted transversely in its middle, then widening again towards the trumpet-shaped aperture. The distal part of the ultimate whorl is turned upward along the spire and adnate to it. The free edge of the peristome reaches somewhat above the top of the shell. Aperture facing back, thus giving a false suggestion of a sinistral shell. Suture deep. umbilicus open, narrow, in some specimens hidden by the deviating part of the last whorl. aperture round, oblique. Peristome continuous, circular, with a wing-like collar behind the peristome and parallel to it. Operculum unknown."