Tornidae is a family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 of very small and minute sea snail

Sea snail

Sea snail is a common name for those snails that normally live in saltwater, marine gastropod molluscs....

s with an operculum

Operculum (gastropod)

The operculum, meaning little lid, is a corneous or calcareous anatomical structure which exists in many groups of sea snails and freshwater snails, and also in a few groups of land snails...

, 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 clade Littorinimorpha

Littorinimorpha

Littorinimorpha is a large clade of gastropods within Hypsogastropoda consisting primarily of marine species, but also aquatic and terrestrial species as well....

. This family used to be known as the Vitrinellidae.

General characteristics

The shells

Gastropod shell

The gastropod shell is a shell which is part of the body of a gastropod or snail, one kind of mollusc. The gastropod shell is an external skeleton or exoskeleton, which serves not only for muscle attachment, but also for protection from predators and from mechanical damage...

 of the snails in this family are minute, colorless and glassy.

The paucispiral shell is umbilicated, auriform and depressed The entire aperture

Aperture (mollusc)

The aperture is an opening in certain kinds of mollusc shells: it is the main opening of the shell, where part of the body of the animal emerges for locomotion, feeding, etc....

 is oblique. It has a simple columella, and a rounded, sharp outer lip

Lip (gastropod)

In the shell of a gastropod mollusk , the margin of the aperture is called the lip or the peristome. In other words, this is a term used to describe part of gastropod shell anatomy....

. The corneous operculum

Operculum (gastropod)

The operculum, meaning little lid, is a corneous or calcareous anatomical structure which exists in many groups of sea snails and freshwater snails, and also in a few groups of land snails...

 is paucispiral and has an excentric nucleus.

The body of the animal differs from species in the family Trochidae

Trochidae

The Trochidae, common name top snails, are a taxonomic family of very small to large sea snails, marine gastropod molluscs in the clade Vetigastropoda ....

 by having no cirriform appendages of the foot.

Subfamilies

The following subfamilies have been recognized in the 2005 taxonomy of Bouchet & Rocroi

Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005)

The taxonomy of the Gastropoda as it was revised by Philippe Bouchet and Jean-Pierre Rocroi is currently the most up-to-date overall system for classifying gastropod mollusks...

:

• Circulinae Fretter & Graham, 1962
• Torninae Sacco, 1896 (1884)
• Teinostomatinae Cossmann, 1917
• Vitrinellinae Bush, 1897

Genera

Genera in the family Tornidae include:

Subfamily Vitrinellinae

• Cyclostremiscus

Subfamily Circulinae

• Circulus
  Circulus (gastropod)
  Circulus is a genus of very small and minute sea snails with an operculum, marine gastropod mollusks in the family Tornidae.-Species:According to the World Register of Marine Species , the following species with valid names are included within the genus Circulus * Circulus congoensis * Circulus...
  
  

Subfamily ?

• Cochliolepis Stimpson, 1958
• Elachorbis
  Elachorbis
  Elachorbis is a genus of minute sea snails or micromolluscs, marine gastropod molluscs in the family Tornidae.- Taxonomy :The exact placement of this genus has long been contested....
  
  Iredale, 1914
• Naricava Hedley, 1913
• Ponderinella
• Pseudoliotina
• Pygmaeorota
• Sigaretornus
• Tornus Turton & Kingston, 1830