Discartemon megalostraka Siriboon & Panha 2014

Shell. Shell globose-heliciform, white and translucent; whorls 7–7½, spire elevated conical, with a distinct suture. Shell surface glossy with fine transverse ridges that diminish below periphery; varices present. Embryonic shell large, about 2½ whorls, with a smooth surface; following whorls regularly coiled. Last whorl rounded and regularly expanded; umbilicus widely open and deep. Aperture sub-quadrangular; peristome discontinuous, thickened, expanded and reflected. Apertural dentition of one strong parietal, one small upper palatal, one palatal, one basal, one columellar and one small supracolumellar lamella (Fig. 10A). Radula. Each row consists of 19–21 teeth with formula (9-10)-1-(9-10). The central tooth is small and triangular with a pointed cusp. Lateral and marginal teeth are undifferentiated and large, unicuspid and lanceolate. Latero-marginal teeth gradually reduce in size, with outermost teeth much smaller and shorter than inner teeth (Fig. 22G). Genital organs. Atrium (at) very short. Penis (p) very long and slender. Penial sheath (ps) thin, extending about third-fourths of penis length. Penial sheath retractor muscle (psr) very thin, originating at genital orifice wall and inserting distally on penial sheath (Fig. 16A). Vas deferens (vd) passes a very short distance through penial sheath before entering into penis distally (Fig. 16B). Penial retractor muscle (pr) thin and long, inserting at penis and vas deferens junction. Internal wall of atrium with large atrial pores (Fig. 21A). Penial wall with scattered and transparent penial hooks, about 9 hooks/200 µm2 (Fig. 21B). Hooks located on penial wall. Penial hooks small (<0.02 mm in length), expanded at base, tips pointed and curved towards genital orifice (Fig. 21C–E). Vagina (v) very short. Gametolytic duct (gd) a long and narrow tube extending as far as albumin gland; gametolytic sac (gs) ovate. Free oviduct (fo) extremely long, proximal part a straight cylindrical tube, distal part corrugated. Oviduct (ov) enlarged and folded; prostate gland inconspicuous. Talon (ta) small, very short and club shaped. Hermaphroditic duct (hd) bearing a long seminal vesicle (sv) about four times as long as the length from talon to branching point of seminal vesicle (Fig. 16C). Vaginal wall with longitudinal vaginal folds (Fig. 21F).

This species is known from several limestone hills in southern Thailand, particularly in the western part of the southern mainland. The animals can be found at altitudes up to 20 meters amsl.