Trissexodon constrictus
Trissexodon constrictus is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusc in the family Trissexodontidae.
Trissexodon constrictus is the type species of the genus Trissexodon.
Distribution
This species endemic to the western Pyrenees and the Basque Country across 29 recorded localities, being recorded in Spain and in France,.Description
The shell is finely and regularly ribbed. It is strongly depressed on the upper side. The lower side is rounded. The shell has 5-6 whorls. The aperture has a characteristic shape. The lip is reflected and forms a "U" shape when seen from above. The umbilicus is deep and covers 1/7 of the shell diameter.The width of the shell is 6–8 mm; the height of the shell is 3–4 mm.