Acteon spec 4

(Figure 12)

Material. Tiep2 (1) RGM 961.770, Tiep5 (1) RGM 961.847.

Characterization. Shell small, tall, with flattened sides; H 1.75 mm, W 1.12 mm; protoconch slightly elevated, 1.2 whorl, DP 0.71 mm; nucleus small, DN 0.25 mm; lower two-thirds of teleoconch whorls sculpted with fine punctuated spiral grooves, becoming stronger towards base; interspaces large, becoming smaller towards base; two separate weak punctuated spiral grooves present on upper one-third of first teleoconch whorl; suture weakly channeled with punctuated spiral groove broader than grooves on rest of whorl; aperture narrow; columella with weak single fold; umbilicus very narrow.

Remarks. This species is distinguished from Acteon spec 1 by the presence of weak punctuated spiral ribs on the upper one-third of teleoconch whorls. All species within Acteonidae, of which material is well described and illustrated, differ from the species discussed here in their sculptural details.