Hyperaulax ridleyi is a species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 of tropical air-breathing land snail

Snail

Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...

, a terrestrial

Terrestrial animal

Terrestrial animals are animals that live predominantly or entirely on land , as compared with aquatic animals, which live predominantly or entirely in the water , or amphibians, which rely on a combination of aquatic and terrestrial habitats...

 pulmonate gastropod mollusk in the family Bulimulidae

Bulimulidae

Bulimulinae is a taxonomic subfamily of medium-sized to large, air-breathing, tropical and sub-tropical land snails, terrestrial pulmonate gastropod molluscs in the family Orthalicidae, according to the taxonomy of the Gastropoda ....

.

Hyperaulax ridleyi is the type species

Type species

In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...

 of the genus Hyperaulax.

This species is native to, and its occurrence is restricted to, Fernando de Noronha

Fernando de Noronha

Fernando de Noronha is an archipelago of 21 islands and islets in the Atlantic Ocean, offshore from the Brazilian coast. The main island has an area of and had a population of 3,012 in the year 2010...

, an island off the coast of Brazil. The snail was described in 1890 by Edgar Albert Smith

Edgar Albert Smith

Edgar Albert Smith was a British zoologist, a malacologist.His father was the Frederick Smith, a well-known entomologist, and Assistant Keeper of Zoology in the British Museum, Bloomsbury...

, a zoologist with the British Museum

British Museum

The British Museum is a museum of human history and culture in London. Its collections, which number more than seven million objects, are amongst the largest and most comprehensive in the world and originate from all continents, illustrating and documenting the story of human culture from its...

. The type specimen is stored in the British Museum of Natural History.

Shell 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 umbilicated, ovate, conic above, moderately solid, brown with a buff line at the periphery, very delicately sculptured with lines of growth, and sometimes has low wrinkles and fine impressed spiral striae. The spire

Spire (mollusc)

A spire is a descriptive term for part of the coiled shell of mollusks. The word is a convenient aid in describing shells, but it does not refer to a very precise part of shell anatomy: the spire consists of all of the whorls except for the body whorl...

 of the shell is conic. The apex

Apex (mollusc)

Apex is an anatomical term for the tip of the mollusc shell of a gastropod, scaphopod, or cephalopod mollusc.-Gastropods:The word "apex" is most often used to mean the tip of the spire of the shell of a gastropod...

 is obtuse. The scuplture

Sculpture (mollusc)

The sculpture of a mollusc shell is the three-dimensional ornamentation on the outer surface, as distinct from the basic shape of the shell itself or colouration. Sculpture may be concave as well as convex. Sometimes it has microscopic detail. Sculpture refers to the calcareous outer layer, not the...

 of the nepionic 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 whorls immediately following the embryonic whorls) has superficial vermiculate (worm-like) wrinkles. The shell has 5½ slightly convex whorls. The last whorl is a little descending and then slightly ascending in front, distinctly constricted behind the peristome. The base of the shell is perforated by a deep and conspicuous, though not wide, umbilicus.

The shell 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 ovate, and is a fleshy-brown color inside. There is a pale median line in half the length of the shell. The peristome is flatly reflexed throughout. The outer lip is subangularly arcuate above, terminations joined by a thin or thick parietal callus, which is thickened and somewhat tubercular above, separated by a vertical groove or channel from a similar callous lobe on the outer lip, near its insertion.

The width of the shell is 6.2-7.2 mm. The height of the shell is 10.5-12.5 mm. The height of the aperture is 5.2-6.2 mm. The width of the type specimen is 5.9. The height of the type specimen is 11.4.