Thelyssina

Helwerda, Renate Ariane, Wesselingh, Frank Pieter & Williams, Suzanne T., 2014, On some Vetigastropoda (Mollusca, Gastropoda) from the Plio-Pleistocene of the Philippines with descriptions of three new species, Zootaxa 3755 (2), pp. 101-135 : 114

Thelyssina ? spec. 2

( Figures 23–25 )

Material. AndaDeVos (10).

Characterization. Shell minute, H 0.8 mm, W 0.7 mm, trochiform, turreted; DN 0.11 mm; P/T boundary thin varix at 1.1 whorls; second varix at 1.6 whorls; T whorls shouldered, with axial lirae and minute pits; body whorl with rounded shoulder and low spiral rib; aperture subquadrate; very thin nacre observed at the damaged outer lip of one specimen; umbilicus narrow, with spiral rib inside.

Remarks. This seguenzioid skeneimorph species is also provisionally placed in Thelyssina , based on the presence of minute pits, a well defined angular shoulder, a basal spiral rib, an umbilical spiral rib and a small protoconch with anastomosing sculpture and a shape similar to the protoconch of the type species for the genus. However, this assignment is open to further scrutiny as Thelyssina ? spec. 2 is relatively tall and lacks dendritic sculpture.

Figures

FIGURES 18 – 25. Seguenziidae. 18. Calliobasis lapulapui Poppe, Tagaro & Dekker, 2006. RGM 608.251. Locality Anda 1. (a) rear view, (b) apertural view, (c) side view, (d) basal view, (e) apical view. 19. Calliobasis lapulapui Poppe, Tagaro & Dekker, 2006. RGM 608.252. Locality Anda 3. (a) SEM, side view, (b) SEM detail of protoconch. 20. Thelyssina? spec. 1. RGM 608.263. Locality Anda 2. (a) rear view, (b) apertural view, (c) basal view, (d) apical view. 21. Thelyssina? spec. 1. RGM 608.264. Locality Anda 2. (a) SEM detail of protoconch, (b) SEM, side view. 22. Thelyssina? spec. 1. RGM 608.265. Locality Anda 2. SEM, basal view. 23. Thelyssina? spec. 2. RGM 608.268. Locality AndaDeVos. (a) rear view, (b) apertural view, (c) basal view, (d) apical view. 24. Thelyssina? spec. 2. RGM 608.269. Locality AndaDeVos. SEM detail of protoconch. 25. Thelyssina? spec. 2. RGM 608.270 Locality AndaDeVos. SEM, basal view.