Odostomia helga
Encyclopedia
Odostomia helga is a species
of sea snail
, a marine
gastropod mollusk in the family
Pyramidellidae
, the pyrams and their allies.
are smooth, deeply obliquely immersed in the first of the succeeding whorls, above which only a portion of the last two volutions project. The six post-nuclear whorls are moderately rounded, slightly contracted at the sutures, feebly shouldered at the summits. They are marked between the sutures by four broad low spiral bands which are separated by narrow, deeply incised lines. In addition to these bands, the first three and one-half whorls are marked by feeble axial ribs which are best developed near the summit of the whorls and scarcely reach the suture. The junction of the ribs and the cords form weak nodules. The sutures are strongly impressed but not channeled. The periphery of the body whorl
is well rounded, marked by a low spiral cord. The base of the shell is strongly rounded posteriorly and attenuated anteriorly. It is marked by seven spiral cords, which grow successively weaker from the periphery toward the umbilical region and are separated by slender, deeply-incised spiral lines. The aperture
is large and broadly oval. The posterior angle is acute. The outer lip
is thin, showing the external sculpture
within. The columella is moderately strong, curved, reflected, and reinforced by the base. It is provided with an oblique fold at its insertion.
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 conic shell is milk-white. It measures 4.2 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...
are smooth, deeply obliquely immersed in the first of the succeeding whorls, above which only a portion of the last two volutions project. The six post-nuclear whorls are moderately rounded, slightly contracted at the sutures, feebly shouldered at the summits. They are marked between the sutures by four broad low spiral bands which are separated by narrow, deeply incised lines. In addition to these bands, the first three and one-half whorls are marked by feeble axial ribs which are best developed near the summit of the whorls and scarcely reach the suture. The junction of the ribs and the cords form weak nodules. The sutures are strongly impressed but not 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 well rounded, marked by a low spiral cord. The base of the shell is strongly rounded posteriorly and attenuated anteriorly. It is marked by seven spiral cords, which grow successively weaker from the periphery toward the umbilical region and are separated by slender, deeply-incised spiral lines. 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 large and broadly oval. The posterior angle is acute. 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 sculpture
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...
within. The columella is moderately strong, curved, reflected, and reinforced by the base. It is provided with an oblique fold at its insertion.