Zemacies marginalis explained

Zemacies marginalis is an extinct species of sea snail, a marine gastropod mollusk in the family Borsoniidae.^[1]

Description

(Original description from a single, imperfect specimen) Seven whorls remain on the spire, and there is a protoconch of three whorls. In the first six whorls there are eighteen tubercles on the keel, but the body whorl is smooth. Sutures are prominently bordered in front. All portions of the whorl have prominent spiral striations, including the tubercles. As shown by the growth lines the anal sinus is moderately sharp, but less so than in Zemacies hamiltoni (Hutton, 1905).

This species is closely related to Zemacies hamiltoni, but differs from it in having the prominent border of the suture, more numerous tubercles, and a much more abundant spiral ornamentation both above and below the keel. ^[2]

Distribution

This extinct marine species is endemic to New Zealand and was found in Middle Eocene strata.

References

• Marshall & Murdoch, Transactions and Proceedings of the New Zealand Institute, vol. 52, p. 134, pl. 6, fig. 7
• Maxwell, P.A. (2009). Cenozoic Mollusca. pp. 232–254 in Gordon, D.P. (ed.) New Zealand inventory of biodiversity. Volume one. Kingdom Animalia: Radiata, Lophotrochozoa, Deuterostomia. Canterbury University Press, Christchurch.

External links

• Conchology.be: image

Notes and References

1. Marshall, B. (2015). Zemacies marginalis. In: MolluscaBase (2015). Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=831527 on 2016-04-10
2. https://www.biodiversitylibrary.org/item/22763#page/274/mode/1up Marshall (1918), Fauna of the Hampden Beds; Transactions and proceedings of the New Zealand Institute, vol. 51, p. 231, pl. 17, fig. 10