Chilostoma achates

Chilostoma achates is a species of medium-sized, air-breathing, land snail, a terrestrial pulmonate gastropod mollusk in the family Helicidae, the true snails. IUCN has defined the snail as Near threatened, due to the development of tourism.^[1] The species inhabits high-altitude limestone environments in the eastern Alps, particularly in South Tyrol and the Carnic Alps of northern Italy, where it grows on damp rock faces and ledges maintained by seepage and snowmelt.

Chilostoma achates
Chilostoma achates shells
Conservation status
Near Threatened  (IUCN 3.1)[1]
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Gastropoda
Order:	Stylommatophora
Family:	Helicidae
Genus:	Chilostoma
Species:	C. achates
Binomial name
Chilostoma achates (Rossmässler, 1835)

Taxonomy and nomenclature

Chilostoma achates (Rossmässler, 1835) was first introduced as Helix foetens var. achates, one of several varieties then included under a broadly defined H. foetens. In 1933 Lothar Forcart reclassified it as the subspecies Chilostoma zonatum achates, before Carlo Alzona (1971) restored it to full species rank—a treatment still followed by modern checklists.^[2]

Description

The shell ranges from 17 to 29 mm across and 7 to 12 mm high. Its colour is a pale yellowish horn, usually bearing a single brown band around the periphery and a paler zone just beneath. There are five gently rounded spiral turns (whorls), separated by a shallow groove called the suture. The final whorl widens markedly before the shell's opening, revealing a broad, slightly off-centre umbilicus (the hollow at the shell's base). The aperture (opening) is set at an angle and bordered by a white lip that is turned back slightly.^[2]

Distribution and habitat

This snail occurs in the eastern Alps of northern Italy, with confirmed populations in South Tyrol (Alto Adige) and the Carnic Alps. It inhabits high-altitude limestone environments—sheer or overhanging rock faces, narrow ledges and mixed scree—where continual seepage and residual snowmelt create the damp conditions it requires.^[2]