''Lacuna crassior'' is a species of

sea snail Sea snail is a common name for slow-moving marine gastropod molluscs, usually with visible external shells, such as whelk or abalone. They share the taxonomic class Gastropoda with slugs, which are distinguished from snails primarily by the ...

, a marine

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

mollusk in the family Littorinidae, the winkles or periwinkles.

Distribution

''Lacuna crassior'' is a

circumboreal The Circumboreal Region in phytogeography is a floristic region within the Holarctic Kingdom in Eurasia and North America, as delineated by such geobotanists as Josias Braun-Blanquet and Armen Takhtajan. It is the largest floristic region in t ...

and

subarctic The subarctic zone is a region in the Northern Hemisphere immediately south of the true Arctic, north of humid continental regions and covering much of Alaska, Canada, Iceland, the north of Scandinavia, Siberia, and the Cairngorms. Generally, ...

species that has Britain as its southern limit. It has though be found in the Channel Islands and Roscoff, the edges of its southerly range.

Description

''Lacuna crassior'' is yellow in colour and can grow up to 14 × 10 mm in length. The maximum recorded shell length is 14 mm.Welch J. J. (2010). "The "Island Rule" and Deep-Sea Gastropods: Re-Examining the Evidence". '' PLoS ONE'' 5(1): e8776. . Its body is very similar in shape to the ''

Lacuna vincta ''Lacuna vincta'', commonly known as the northern lacuna, the wide lacuna, the northern chink shell, or the banded chink shell, is a species of sea snail, a marine gastropod mollusk in the family Littorinidae, the winkles or periwinkles. It is ...

'', with a long, broad snout and slender head tentacles. Its foot is elongated, with a double-edged anterior margin and two short, white, metapodial tentacles projecting from below the operculum. These metapodial tentacles are less flattened than those of ''Lacuna vincta''. The ''Lacuna crassior'' has a strong shell, with six to seven turreted whorls. Its fine spiral striae and vertical

costae In vertebrate anatomy, ribs ( la, costae) are the long curved bones which form the rib cage, part of the axial skeleton. In most tetrapods, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the c ...

are mostly obscured by thick

periostracum The periostracum ( ) is a thin, organic coating (or "skin") that is the outermost layer of the shell of many shelled animals, including molluscs and brachiopods. Among molluscs, it is primarily seen in snails and clams, i.e. in gastropods and ...

, but form a series of irregular folds on the shell's last whorl. The umbilicus is occasionally closed and the umbilical groove reduced with the aperture drawn out and angulated at the base of the columella.

Habitat

It is uncommon and occurs at low water spring tide (LWST), the lower part of the beach that is uncovered only a few times a month during spring tides. It also occurs offshore at a depths greater than 30 metres and up to 90 m. It can be found among stones within mud, sand, gravel and coarser sediments. Minimum recorded depth is 2 m. Maximum recorded depth is 176 m.

References

{{DEFAULTSORT:Lacuna Crassior Littorinidae Gastropods described in 1803