Trissexodon constrictus is a species of 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...

, a gastropod in the family Trissexodontidae

Trissexodontidae

Trissexodontidae is a family of land snails, gastropods in the superfamily Helicoidea .This family has no subfamilies...

.

Trissexodon constrictus is the type species of the genus Trissexodon.

Distribution

It is found in France and Spain: from western Pyrenees

Pyrenees

The Pyrenees is a range of mountains in southwest Europe that forms a natural border between France and Spain...

 to Biscay

Biscay

Biscay is a province of Spain and a historical territory of the Basque Country, heir of the ancient Lord of Biscay. Its capital city is Bilbao...

. It is endemic species of western Pyrenees.

Description

The 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 finely and regularly ribbed. It is strongly depressed on upper side. The lower side is rounded. The shell has 5-6 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 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 with characteristic shape. The lip is reflected and forming a U when seen from above. Umbilicus is deep and covers 1/7 of shell diameter.

The width of the shell is 6-8 mm. The height of the shell is 3-4 mm.

Ecology

Trissexodon constrictus can be found under stones in the soil of humid and shady forests, between moss and under leaves, from sea level to 800 m, exceptionally 1500 m.

External links

• Tryon G. W. (1895). Manual of Conchology (2)3: page 121. plate 24, figure 38-40.