Topaginella is a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of minute fossil sea snail

Snail

Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...

s, marine

Marine (ocean)

Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...

 gastropod mollusks in the family Cystiscidae

Cystiscidae

Cystiscidae is a taxonomic family of minute sea snails, marine gastropod mollusks or micromollusks.- Description :The shell is minute to large, either white, uniformly colored, or patterned; the surface is smooth, sculptured, or axially costate; the spire is flat to immersed, or low to tall; the...

. Like all of the related genera, this are sometimes still classified in the family Marginellidae

Marginellidae

Marginellidae, or the margin shells, are a taxonomic family of small, often colorful, sea snails, marine gastropod molluscs in the clade Neogastropoda.- Taxonomy :...

.

This genus is extinct.

Shell description

Shell minute, pyriform, strongly narrowed anteriorly; spire

Spire (mollusc)

A spire is a descriptive term for part of the coiled shell of mollusks. The word is a convenient aid in describing shells, but it does not refer to a very precise part of shell anatomy: the spire consists of all of the whorls except for the body whorl...

 low; lip thickned, strongly denticulate; external varix

Varix (mollusc)

A varix is an anatomical feature of the shell of certain sea snails, marine gastropod molluscs.It is a thickened axial ridge in the shell of some families of gastropods. A varix is located at intervals around the whorl, and is formed by considerable thickening of the outer lip at a resting stage...

 probably absent (needs to be confirmed); distinct axial costae present; siphonal notch absent; columella multiplicate, with combined total of usually 8 plications plus parietal lirae.

Type species

The type species of the genus Topaginella is
Marginela octoplicata Tenison Woods

Julian Tenison Woods

Julian Edmund Tenison Woods was an English Roman Catholic priest and geologist, active in Australia. With Saint Mary MacKillop, he helped to found the Sisters of St Joseph of the Sacred Heart at Penola in 1866....

, 1877 †; OD (M)

Remarks: The type species seems to be unique (a monotypic

Monotypic

In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...

 genus). The multiplicate columella and lack of a siphonal notch place it near Cystiscus, but the pyriform shape, exserted spire

Spire (mollusc)

A spire is a descriptive term for part of the coiled shell of mollusks. The word is a convenient aid in describing shells, but it does not refer to a very precise part of shell anatomy: the spire consists of all of the whorls except for the body whorl...

, denticulate lip, and fine axial costae render it distinct.