Plectostoma salpidomon (van Benthem Jutting, 1952)
Shares with Plectostoma laemodes the general shell form, in terms of apex, spire, and tuba shape, but differs by having a tuba that attaches partly to the spire.
Shares with Plectostoma laemodes the general shell form, in terms of apex, spire, and tuba shape, but differs by having a tuba that attaches partly to the spire.
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Holotype: ZMA 136045(1) (Seen). Paratypes: ZMA 136046(>25) (Seen), ZMA 136047(2) (Seen), ZMA 136048(>10) (Seen).
See discussion under Plectostoma laemodes.
Type locality. Gua Bama, Pahang (4°11'37"N, 101°58'2"E) (Figure 18B).
Distribution range. Plectostoma salpidomon can be found in many limestone hills in the valley in between the Titiwangsa, Tahan and Benom mountain ranges (Figure 18B).
Apex. Shape: distinctly convex.
Spire. Height: 2.5–2.8 mm. Width: 1.5–1.7 mm. Number of whorls: 4 5/8–5 1/4. Apical spire shape: depressed conical. Basal spire shape: ovoid. Whorl periphery: moderately to distinctly convex. Umbilicus: completely or partially closed by tuba.
Constriction. Parietal teeth: two. Basal teeth: none.
Tuba. Coiling direction: type 2 and aperture visible in right lateral view. Tuba whorl length in proportion to spire last whorl: ca. 3/4–7/8. Proportion of tuba that attaches to spire: less than 2/3.
Aperture and peristome. Peristome: double peristomes. Outer peristome shape: similar 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: absent. Thin lines: present.
Radial ribs. Rib density: 5–6 ribs per mm. Rib intensity: thin. Shape: slightly curved. Inclination: prosoclin.
Least concern. Plectostoma salpidomon has a wide distribution range. Living populations have been recorded in many limestone hills and some of these are in protected areas.
ZMA 162137(>25), BOR 459(1), BOR 5539(>10), BOR 5540(>10), BOR 5541(5), BOR 5542(>25), BOR 5569(>25), BOR 5611(1), V 8171(4), V 8658(>25), V 8706(6), V 9116(7), V 9292(3).
“The new species is somewhat related to O. (P.) laidlawi, O. (P.) annandalei and O. (P.) decrespignyi, but the spire is more turreted and the free part shorter than in either of these. From O. (P.) tonkinianum Dautz. & Fisch. It differs in the more slender spire and smaller size. Moreover the last whorl is entirely adnate, without free part in O. (P.) tonkinianum.” (Benthem-Jutting, 1952)
Benthem-Jutting (1952) original descriptions on Opisthostoma (Plectostoma) salpidomon – “Shell high-turreted, reddish-brown, yellowish-brown or fawn. First 1 ½ whorl smooth, subsequent ones ornamented with fine white oblique ribs at more or less regular intervals. In fresh condition these ribs stand out wing-like away from the shell. In worn specimens they appear as elevated threads on the whorls. No spiral sculpture between the ribs. Not transparent and only little shining. Whorl 7 ½-8 ½, convex. The first 6 ½-7 ½ regularly increasing in size, the last somewhat constricted at its beginning, then widening again and turning back along the base of the shell as if starting a sinistral spiral. Distal part, just before the aperture ascending, free, like a small trumpet. Top whorls not oblique on the rest of the shell. Suture deep. Umbilicus narrow, in some specimens hidden by the abnormal twist of the last whorl. Aperture vertical or somewhat directed upwards, round. Peristome continuous, almost circular, flanged by a collar-like rib behind the peristome and parallel to it. Operculum unknown.”
“…on renewed investigation, spiral striae proved to be present.” (Benthem-Jutting, 1961)
Opisthostoma (Plectostoma) salpidomon – “Dimensions: Height 3.0-3.4, Breadth 2.4-2.9, Diam. apert. 1.0-1.1 mm.” (Benthem-Jutting, 1952)
Type locality – “Malaya: Gua Bama, near Padang Tengku, Pahang” (Benthem-Jutting, 1952)
Other localities – “Malaya: Gua Tinggi, near Kuala Lipis, Pahang” (Benthem-Jutting, 1952); “Malaya: Goa Siput, near Batu Lompat, Pahang” (Benthem-Jutting, 1952); “Malaya: Gua Che Yatin, Ulu Tembeling, Pahang” (Benthem-Jutting, 1961)