Amphithalamus ornatus

Amphithalamus ornatus
Shell of Amphithalamus ornatus (holotype at the Auckland Museum)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Gastropoda
Subclass:	Caenogastropoda
Order:	Littorinimorpha
Family:	Anabathridae
Genus:	Amphithalamus
Species:	A. ornatus
Binomial name
Amphithalamus ornatus (A. W. B. Powell, 1927)
Synonyms [1]
Amphithalamus (Notoscrobs) ornatus(A. W. B. Powell, 1927) alternative representation Notoscrobs ornatusA. W. B. Powell, 1927 (superseded combination)

Amphithalamus ornatus is a species of minute sea snails, marine gastropod molluscs or micromolluscs in the family Anabathridae. ^[1]

Description

The length of the shell attains 1.3 mm, its diameter 0.8 mm.

(Original description) The shell is minute, solid, conical, and imperforate. The protoconch is dome-shaped, consisting of 1 1/2 whorls, and is sculptured with about twelve spiral rows of minute, round, shallow pits spaced alternately with those of the rows immediately above and below, thus giving a honeycomb effect.

The shell consists of 4 1<2 whorls. The spire is conic with straight outlines. The spire-whorls are sculptured with two spiral keels, the upper one being crossed by slightly oblique strong axial ribs. The body whorl features an additional three plain spiral keels on its base.

The aperture is oblique and oval, slightly constricted above. The peristome is duplicated and continuous, with a smooth, raised inner margin surrounded by an expanded, slightly concave area, which is widest above and on the parietal wall, with its outer edge bounded. ^[2]

Distribution

This species is endemic to New Zealand and occurs off the north-eastern North Island as far south as Mayor Island.

References

1. Amphithalamus ornatus (A. W. B. Powell, 1927) . 24 May 2025. Retrieved through: World Register of Marine Species .
2. Powell, A.W.B. (1927). "The genetic relationships of Australasian rissoids. Part 1. Descriptions of new recent genera and species from New Zealand and the Kermadec Islands". Transactions and Proceedings of the New Zealand Institute. 57: 548. Retrieved 24 May 2025. This article incorporates text from this source, which is in the public domain .

• Powell, A.W.B. 1979 New Zealand Mollusca: Marine, Land and Freshwater Shells, Collins, Auckland
• Spencer, H.G., Marshall, B.A. & Willan, R.C. (2009). Checklist of New Zealand living Mollusca. Pp 196-219. in: Gordon, D.P. (ed.) New Zealand inventory of biodiversity. Volume one. Kingdom Animalia: Radiata, Lophotrochozoa, Deuterostomia. Canterbury University Press, Christchurch.