Microcystina paripari sp. nov. Figures 28B, 30A-F

Material examined.

Holotype (SH 1.25 mm, SW 2.08 mm) (MZU.MOL.20.12), Malaysia, Sarawak, Kuching Division, Fairy Caves (Site 2), south part of Gunung Kapor, 4 miles SW Bau, 1°22'56.09"N, 110°6'58.82"E, coll. M. E. Marzuki, 7.I.2018 . Paratypes: 2 ex. (MZU.MOL.20.13), 7 ex. (ME0009647), same data as the holotype;> 10 ex. (ME0009329), the same locality, coll. M. E. Marzuki, 8.IV.2017; 1 ex. (ME0003845), Fairy Caves (Site 1), south part of Gunung Kapor, 4 miles SW Bau, 1°22'53.76"N, 110°7'4.34"E, coll. M. E. Marzuki, 11.III.2011 ; 2 ex. (ME0009469), the same locality, coll. M. E. Marzuki, 8.IV.2017; 2 ex. (ME0008510), the same locality, coll. M. E. Marzuki, 10.II.2017; 2 ex. (ME0001761), the same locality, coll. M. E. Marzuki, 23.VI.2010; 1 ex. (ME0001749), Gunung Doya, limestone hill near Sungai Sebuyoh, 3.4 miles SE Bau, 1°22'57.24"N, 110°11'39.42"E, coll. M. E. Marzuki, 10.VII.2011 ; 1 ex. (ME0009677), Bukit Sokwang (Site 3), northern site of Gunung Doya, limestone hill along Skio road, 2.05 miles E Bau, 1°23'49.87"N, 110°10'32.14"E, coll. M. E. Marzuki, 7.I.2018 ; 37 ex. (ME0009044), Buddha Caves (Site 3), north part of Gunung Kapor, 3 miles SW Bau, 1°23'26.51"N, 110°7'10.02"E, coll. M. E. Marzuki, 9.IV.2017 ; 1 ex. (ME0000783), Gunung Batu, limestone outcrop along Skio road, Jambusan, 2.4 miles E Bau, 1°23'50.65"N, 110°11'19.99"E, coll. M. E. Marzuki, 11.III.2011 ;> 10 ex. (ME0001746), same locality, coll. M. E. Marzuki, 10.VII.2011 .

Differential diagnosis.

It differs from Microcystina muscorum Van Benthem-Jutting, 1959 and Microcystina gratilla Van Benthem-Jutting, 1950 in having a shell without spiral striations on both the protoconch and teleoconch.

Description.

Shell very small, thin, translucent, straw yellow to brown, lenticular, spire moderately elevated. Surface with a glossy lustre. Whorls slightly convex. Number of whorls <4. Protoconch smooth, sometimes with a few inconspicuous, corrugation at the suture. Teleoconch without spiral sculpture. Radial sculpture on teleoconch: inconspicuous growth lines, then next to these with distinct, well-spaced to densely spaced, shallow grooves, sometimes the latter striation is predominant. Aperture lunulate. Peristome simple; somewhat thickened and reflected on columellar side, not thickened nor reflected on basal and palatal side. Umbilicus open, narrow; umbilical region is moderately concave. Dimensions: shell height <1.25 mm; shell width <2.08 mm; diameters of the first three whorls 0.13 mm, 0.21 mm, and 0.25 mm, respectively; aperture height <0.75 mm; aperture width <0.92 mm.

Geographic distribution and habitat.

It is known from the Bau limestone hill clusters only. Only dry shells were found during the surveys.

Etymology.

The specific epithet Microcystina paripari is in reference to the type locality, Gua Pari-pari, and is the Malay word for fairies.