Clanculus johnstoni
A small, carmine top snail endemic to Australian waters.
Clanculus johnstoni is a marine gastropod mollusk in the family Trochidae, commonly known as a top snail. This small, sturdy sea snail has a globose-conic shell that reaches 6 mm in both height and major diameter. Its shell is typically carmine with about eight radial buff dashes per whorl, extending from the suture halfway to the periphery. The umbilicus and bordering funicle are white. A color dimorphism exists in which olive brown replaces the carmine, though a trace of carmine remains at the shell's summit. The shell has five whorls; the penultimate whorl features four spirals, with the uppermost being a double bead row, and a fifth spiral half-buried in the suture. On the body whorl, thirteen spirals become taller, broader, and more widely spaced as they rise from base to suture, often breaking into beads. The oblique aperture ascends toward the end, with about a dozen entering ridges inside the outer lip, the lowest being largest. The columella is oblique and twisted, with a reflected edge bearing a large tooth at its base and a small one above. The umbilical margin broadly overreaches the cavity, its edge having three or four denticules, and a translucent callus unites the lips. This species is endemic to Australia, found at intertidal depths off the Northern Territory and Queensland.
Quick Facts
- Taxon
- Clanculus johnstoni
Facts from the source article.
Lore & Background
The shell of Clanculus johnstoni has a globose-conic shape and attains a height and major diameter of 6 millimetres. Its carmine color is marked with radial buff dashes, about eight per whorl, reaching from the suture halfway to the periphery. The umbilicus and bordering funicle are white. A color dimorphism occurs in which olive brown replaces the carmine, with a trace of carmine remaining on the summit.
The shell contains five whorls. On the penultimate whorl there are four spirals, the upper being a double bead row, and a fifth half-buried in the suture by the succeeding whorl. On the body whorl there are thirteen spirals that become taller, broader, more widely spaced, and more inclined to break up into beads as they ascend from base to suture. The oblique aperture is finally ascending, and within the outer lip are about a dozen entering ridges, the lowest larger than the rest. The oblique columella is twisted, with the edge reflected, bearing a large tooth at the base and a small one above. The umbilical margin broadly overreaches the cavity, its edge with three or four denticules, and a translucent callus unites the lips.
Reader's Guide
Clanculus johnstoni is a marine gastropod mollusk in the family Trochidae, documented in Australian marine shell references. Its description includes detailed shell morphology such as the number and arrangement of spirals, the structure of the aperture and columella, and the presence of a color dimorphism. The species is endemic to Australia, occurring at intertidal depths off the Northern Territory and Queensland. The source article provides no further information on its significance or legacy beyond these morphological and distributional facts.
Did You Know?
- The shell height and major diameter are both 6 mm.
- The shell has a carmine color with radial buff dashes, about eight per whorl.
- A color dimorphism exists where olive brown replaces the carmine.
- The body whorl has thirteen spirals that become taller and broader toward the suture.
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