Apex. Shape: distinctly convex.
Spire. Height: 2.0–2.2 mm. Width: 1.8–2.0 mm. Number of whorls: 4 1/4–4 5/8. Apical spire shape: depressed conical. Basal spire shape: conical. Whorl periphery: moderately to distinctly convex. Umbilicus: open.
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. 5/8–7/8. Proportion of tuba that attaches to spire: more than 1/3 but less than 1/2.
Aperture and peristome. Peristome: double peristomes. Outer peristome shape: similar to inner peristome, projected all around, except the posterior part, where the left lateral sides are slightly more projected than the anterior and right lateral side.
Spiral lines. Thick lines: absent. Thin lines: present.
Radial ribs. Rib density: 6–7 ribs per mm. Rib intensity: thin. Shape: slightly curved. Inclination: moderately prosoclin.
to be added
Holotype: ZMA 136034(1) (Seen). Paratypes: ZMA 136041(>50) (Seen), ZMA 136042(>25) (Seen).
There is no genetic information for Plectostoma praeco. Morphological similarity suggests thatPlectostoma praeco and Plectostoma tenggekensis are closely related. Each of the two species has a narrow distribution range and they are separated from each other by at least 50 km.
Type locality. Batu Che Derani, Taman Negara Pahang (4°35'57"N, 102°25'57"E).
Distribution range. Plectostoma praeco has been recorded from four other hills at upper Sungai Keniyam Kecil, which is in the vicinity of the type locality (Figure 18B).