Odostomia effusa
Encyclopedia
Odostomia effusa is a species
of sea snail
, a marine
gastropod mollusk in the family
Pyramidellidae
, the pyrams and their allies.
are small, smooth, and almost completely obliquely immersed in the first of the succeeding turns, above which only the tilted edge of the last volution projects. The six post-nuclear whorls are flattened, strongly contracted at the sutures and moderately shouldered at the summit. They are marked by strong, tuberculate retractive axial ribs, of which 18 occur upon the first and second and 20 upon the remaining turns. In addition to these axial ribs the whorls are marked by four slender, spiral cords between the sutures, which pass over the axial ribs and render them tuberculate at their junction. The spaces enclosed by the ribs and cords are rectangular pits, which have their long axis parallel with the spiral cords. The sutures are channeled. The periphery of the body whorl
is marked by a spiral groove. The
base of the body whorl is well rounded, and marked by eight spiral cords which grow successively weaker and closer spaced from the periphery to the umbilical area. The wide grooves between the spiral cords are marked by slender, raised, axial threads, which correspond to the ribs on the spire
. The aperture
is ovate and somewhat effuse anteriorly. The posterior angle is obtuse. The outer lip
is thin, showing the external markings within. The columella is stout, strongly reflected, and provided with a slender fold at its insertion. The parietal wall is covered by a strong callus.
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
Marine (ocean)
Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...
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...
Pyramidellidae
Pyramidellidae
Pyramidellidae, common name the pyram family, or pyramid shells, is a voluminous taxonomic family of mostly small and minute ectoparasitic sea snails, marine heterobranch gastropod molluscs or micromolluscs....
, the pyrams and their allies.
Description
The elongate-conic shell is vitreous. It measures 2.8 mm. The nuclear whorlsWhorl (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...
are small, smooth, and almost completely obliquely immersed in the first of the succeeding turns, above which only the tilted edge of the last volution projects. The six post-nuclear whorls are flattened, strongly contracted at the sutures and moderately shouldered at the summit. They are marked by strong, tuberculate retractive axial ribs, of which 18 occur upon the first and second and 20 upon the remaining turns. In addition to these axial ribs the whorls are marked by four slender, spiral cords between the sutures, which pass over the axial ribs and render them tuberculate at their junction. The spaces enclosed by the ribs and cords are rectangular pits, which have their long axis parallel with the spiral cords. The sutures are channeled. The periphery of the body whorl
Body whorl
Body whorl is part of the morphology of a coiled gastropod mollusk.- In gastropods :In gastropods, the body whorl, or last whorl, is the most recently-formed and largest whorl of a spiral or helical shell, terminating in the aperture...
is marked by a spiral groove. The
base of the body whorl is well rounded, and marked by eight spiral cords which grow successively weaker and closer spaced from the periphery to the umbilical area. The wide grooves between the spiral cords are marked by slender, raised, axial threads, which correspond to the ribs on 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...
. 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 ovate and somewhat effuse anteriorly. The posterior angle is obtuse. The outer lip
Lip (gastropod)
In the shell of a gastropod mollusk , the margin of the aperture is called the lip or the peristome. In other words, this is a term used to describe part of gastropod shell anatomy....
is thin, showing the external markings within. The columella is stout, strongly reflected, and provided with a slender fold at its insertion. The parietal wall is covered by a strong callus.