Bayerotrochus westralis, commonly known as "Australia's split shell", 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 sea snail

Sea snail

Sea snail is a common name for those snails that normally live in saltwater, marine gastropod molluscs....

, a marine gastropod mollusk in the family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Pleurotomariidae

Pleurotomariidae

Pleurotomariidae, common name the '"slit snails", is a family of large marine gastropods in the clade Vetigastropoda. This family is very ancient; there were numerous species in the geological past. It is currently represented by a group of species that live only in deep water...

.

Description

The shell has a turbinate shape with an apical spire angle of approximately 90 degrees, with inflated body whorls that are proportionate in expansion so that the spire profile is straight, a clearly defined suture, and the periphery is oblique and slightly rounded. The base is highly inflated and lacks a columellar callus at the center of the base area. The 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 oval, the slit is positioned roughly one third of the way between the upper and lower sutures and is relatively long, about 19 percent of the circumference. The shell is lightly sculptured with very numerous fine spiral cords above and below the selenizone (the area where the shell growth filled in the slit), crossed by very numerous fine axial growth lines. The base has very numerous spiral striae which are crossed by numerous radial growth lines. The protoconch

Protoconch

A protoconch is an embryonic or larval shell of some classes of molluscs, e.g., the initial chamber of an ammonite or the larval shell of a gastropod...

 and primary whorls are white and the main body whorls are a pale buff to white color with an iridescent coppery metalic sheen. Occasionally the teleoconch (body whorls) are overlaid with pale orange or pink axial flammules. The selenizone has no distinct spiral sculpture however it has numerous fine curved growth striae. The base is the same base color as the body, and the interior of the aperture is thinly nacreous (pearly). This species is often found without a periostracum

Periostracum

The periostracum is a thin organic coating or "skin" which is the outermost layer of the shell of many shelled animals, including mollusks and brachiopods. Among mollusks it is primarily seen in snails and clams, i.e. in bivalves and gastropods, but it is also found in cephalopods such as the...

. The operculum

Operculum (gastropod)

The operculum, meaning little lid, is a corneous or calcareous anatomical structure which exists in many groups of sea snails and freshwater snails, and also in a few groups of land snails...

 is circular, light brown, multispiral, and chitinous. Size range: 44 to 130 mm diameter.

Distribution

This species has been typically found on soft muddy bottoms between 250 and 500 meters in a small area off West Australia south of Broome

Broome

-Places:Australia*Broome, Western Australia**Attack on Broome **Broome Bird Observatory**Broome Bulls, Australian Rules football team**Broome International Airport**Broome Pearling Lugger Pidgin**Broome race riots of 1920**Broome Regional Prison...

 and northwards to the Ashmore Reefs.

External links

• Gastropods.com image at: http://www.gastropods.com/8/Shell_4448.shtml