Thelyssina ? spec. 1

(Figures 20–22)

Material. Anda 2 (5); AndaDeVos (2).

Characterization. Shell minute, H 0.8 mm, W 0.7 mm; P 1.1 whorls, with fine anastomosing sculpture, DN 0.08 mm; P/T boundary rounded varix; second varix at 1.6 whorls; T whorls with a sharp keel; microsculpture granulate; body whorl with two sharp spiral ribs; aperture rounded; umbilicus narrow; umbilical ridge weak.

Remarks. This seguenzioid skeneimorph species is provisionally placed in Thelyssina, based on the presence of dendritic teleoconch sculpture and a keeled shoulder. At the highest magnifications available, we observed very brilliantly shiny shell material at the inner side of the outer lip that we interpret as nacre. The small protoconch is also similar to the protoconch of the type species for the genus, T. sterrha Marshall, 1983, in the anastomosing sculpture and characteristic shape. However, this assignment is uncertain, because the fossil species is relatively tall and more strongly granulate and keeled. Thelyssina ? spec. 1 also resembles Conotalopia minima (Golikov, 1967), a Recent trochid species from Japan, in general shape, but it has a smaller protoconch relative to the first teleoconch whorl, a dendritic granulate sculpture on the teleoconch and a narrower umbilicus.