Achatinella taeniolata, an O'ahu tree snail, is a species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 of colorful, tropical, tree-living, air-breathing land snail

Land snail

A land snail is any of the many species of snail that live on land, as opposed to those that live in salt water and fresh water. Land snails are terrestrial gastropod mollusks that have shells, It is not always an easy matter to say which species are terrestrial, because some are more or less...

, an arboreal pulmonate gastropod mollusk in the family Achatinellidae

Achatinellidae

Achatinellidae is a family of tropical air-breathing land snails, terrestrial pulmonate gastropod mollusks in the superfamily Achatinelloidea.- Taxonomy :...

.

This taxon is a subspecies of Achatinella viridans

Achatinella viridans

Achatinella viridans is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species is endemic to the United States.-Shell description :...

as there is a complete intergradation

Intergradation

In zoology, intergradation is the way in which two distinct subspecies are connected via areas where populations are found that have the characteristics of both...

 between them.

Shell description

The dextral shell

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...

 is ovate-oblong, spiro-conic, solid, striatulate. The shell is more obsolete toward the apex

Apex (mollusc)

Apex is an anatomical term for the tip of the mollusc shell of a gastropod, scaphopod, or cephalopod mollusc.-Gastropods:The word "apex" is most often used to mean the tip of the spire of the shell of a gastropod...

 and with slightly convex whorls

Whorl (mollusc)

A whorl is a single, complete 360° revolution or turn in the spiral growth of a mollusc shell. A spiral configuration of the shell is found in of numerous gastropods, but it is also found in shelled cephalopods including Nautilus, Spirula and the large extinct subclass of cephalopods known as the...

. The shell has six whorls. Shell colors are glossy white ornamented with varying brown bands. The white columella is strongly toothed above and the margin is dilated, reflexed and appressed. The white 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 irregularly semioval. The peristome is narrowly thickened outside, and strongly lipped within.

The height of the shell is 20.0 mm. The width of the shell is 11.0 mm.

Distribution

This species is endemic

Endemic (ecology)

Endemism is the ecological state of being unique to a defined geographic location, such as an island, nation or other defined zone, or habitat type; organisms that are indigenous to a place are not endemic to it if they are also found elsewhere. For example, all species of lemur are endemic to the...

 to the Hawaiian island of O`ahu.