Seguenzia donaldi Ladd, 1982

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 : 108

Seguenzia donaldi Ladd, 1982

( Figures 8–9 )

1982 Seguenzia donaldi nov. spec.—Ladd: p. 32–33, pl. 35, figs 9–15.

Material. Anda 6 (6); AndaDeVos (29); AndaClif3 (10).

Characterization. Shell relatively broad conical to trochiform, H 1.9 mm, W 1.9 mm; P small, 1.1 whorls; nucleus weakly inclined, DN 0.11–0.14 mm; P/T boundary weak; T with numerous sigmoid axial lirae fading on later T whorls; relatively wide body whorl with three peripheral spiral ribs and five to seven basal spiral ribs; upper apertural retraction deep, upper projection strongly expanding forwards; basal columellar fold or tooth present; umbilicus narrow.

Distribution. Apart from the studied material, this species is known from Pleistocene deposits of Vanuatu ( Ladd 1982).

Differentiation. This species is rather similar to S. trochiformis Poppe, Tagaro & Dekker, 2006 , in having a strong tooth on the columella and an aperture with projections and retractions. However, S. trochiformis has a higher spire (H/W ratio of holotype Poppe et al., 2006: 1.10; H/W ratio of S. donaldi 1.02-1.07 (table 2)) and a less swollen body whorl. Seguenzia donaldi differs from S. cf. keikoae by its wider whorls. The keel in S. donaldi is stronger, its axial lirae are weaker, the protoconch less inclined, the base of the body whorl flatter and the umbilicus wider.

Figures

FIGURES 8 – 12. Seguenziidae. 8. Seguenzia donaldi Ladd, 1982. RGM 608.215. Locality AndaDeVos. (a) rear view, (b) apertural view, (c) side view, (d) basal view, (e) apical view. 9. Seguenzia donaldi Ladd, 1982. RGM 608.216. Locality Anda 3. (a) rear view, (b) apertural view. 10. Seguenzia cf. elegantissima Poppe, Tagaro & Dekker, 2006. RGM 608.221. Locality AndaDeVos. (a) rear view, (b) apertural view, (c) side view, (d) basal view, (e) apical view. 11. Seguenzia cf. elegantissima Poppe, Tagaro & Dekker, 2006. RGM 608.222. Locality AndaDeVos. (a) rear view, (b) apertural view, (c) spire. 12. Seguenzia cf. elegantissima Poppe, Tagaro & Dekker, 2006. RGM 608.223. Locality AndaDeVos. SEM detail of protoconch.