Odostomia communis
Encyclopedia
Odostomia communis is a species
of sea snail
, a marine
gastropod mollusk in the family
Pyramidellidae
, the pyrams and their allies.
number at least two, forming a depressed helicoid spire, whose axis is at right angles to that of the succeeding turns, in the first of which it is all but one-half immersed. The seven post-nuclear whorls are flattened, strongly contracted at the suture and decidedly shouldered at the summit. They are marked by strong vertical axial ribs of which there are 16 upon the first and second, 18 upon the third to fifth, and 20 upon the penultimate turn. In addition to the ribs the whorls are marked by four spiral cords about one-half as strong as the ribs, between the sutures: the first of these is at the angle of the shoulder. The junction of the spiral cords and ribs are nodulous. The spaces enclosed between them are rectangular pits. The sutures are channeled. The periphery of the last whorl is marked by a spiral cord at whose posterior margin the axial ribs terminate. The base produced is moderately rounded, marked by ten spiral cords, which, like the grooves separating them, decrease regularly in size from the periphery to the umbilical area. The grooves on the base are crossed by numerous slender axial threads. The aperture
is pyriform, somewhat effuse anteriorly. It is channeled at the posterior angle, which is obtuse. The outer lip
is thin, with a simple edge, decidedly arched in the middle, flattened on the side, showing the external sculpture within. The columella is stout, profoundly but distinctly plaited, reflected very much anteriorly. It is provided with a strong fold at its insertion. The parietal wall is covered with a thick callus. The operculum
is radiately corrugated.
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 small, milk-white shell is pupiform and generally cancellated. It measures 3.2 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...
number at least two, forming a depressed helicoid spire, whose axis is at right angles to that of the succeeding turns, in the first of which it is all but one-half immersed. The seven post-nuclear whorls are flattened, strongly contracted at the suture and decidedly shouldered at the summit. They are marked by strong vertical axial ribs of which there are 16 upon the first and second, 18 upon the third to fifth, and 20 upon the penultimate turn. In addition to the ribs the whorls are marked by four spiral cords about one-half as strong as the ribs, between the sutures: the first of these is at the angle of the shoulder. The junction of the spiral cords and ribs are nodulous. The spaces enclosed between them are rectangular pits. The sutures are channeled. The periphery of the last whorl is marked by a spiral cord at whose posterior margin the axial ribs terminate. The base produced is moderately rounded, marked by ten spiral cords, which, like the grooves separating them, decrease regularly in size from the periphery to the umbilical area. The grooves on the base are crossed by numerous slender axial threads. 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 pyriform, somewhat effuse anteriorly. It is channeled at the posterior angle, which 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, with a simple edge, decidedly arched in the middle, flattened on the side, showing the external sculpture within. The columella is stout, profoundly but distinctly plaited, reflected very much anteriorly. It is provided with a strong fold at its insertion. The parietal wall is covered with a thick callus. 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 radiately corrugated.