''Zemacies marginalis'' is an extinct species of

sea snail Sea snail is a common name for slow-moving marine gastropod molluscs, usually with visible external shells, such as whelk or abalone. They share the taxonomic class Gastropoda with slugs, which are distinguished from snails primarily by the ...

, a marine

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

mollusk in the family

Borsoniidae Borsoniidae is a monophyletic family of small to medium-sized sea snails, marine gastropod mollusks in the superfamily Conoidea.Bouchet, P. (2011). Borsoniidae. Accessed through: World Register of Marine Species at http://www.marinespecies.o ...

.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

Description

(Original description from a single, imperfect specimen) Seven

whorl A whorl ( or ) is an individual circle, oval, volution or equivalent in a whorled pattern, which consists of a spiral or multiple concentric objects (including circles, ovals and arcs). Whorls in nature File:Photograph and axial plane floral ...

s remain on the spire, and there is a

protoconch A protoconch (meaning first or earliest or original shell) is an embryonic or larval shell which occurs in some classes of molluscs, e.g., the initial chamber of an ammonite or the larval shell of a gastropod. In older texts it is also called ...

of three whorls. In the first six whorls there are eighteen tubercles on the keel, but the

body whorl The body whorl is part of the morphology of the shell in those gastropod mollusks that possess a coiled shell. The term is also sometimes used in a similar way to describe the shell of a cephalopod mollusk. In gastropods In gastropods, the b ...

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. Marshall (1918), ''Fauna of the Hampden Beds''; Transactions and proceedings of the New Zealand Institute, vol. 51, p. 231, pl. 17, fig. 10
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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. marginalis Gastropods of New Zealand Gastropods described in 1919 {{Borsoniidae-stub