Odostomia heterocincta
Encyclopedia
Odostomia heterocincta is a species
of sea snail
, a marine
gastropod mollusk in the family
Pyramidellidae
, the pyrams and their allies.
s number at least 2, forming a depressed helicoid spire
, which is obliquely, almost one-half immersed in the first of the succeeding turns. The six post-nuclear whorls are moderately rounded. They are marked by strong, decidedly retractive, axial ribs and, on the first four turns, by three spiral cords which equal the ribs in strength; the middle one of these three cords is a little nearer that at the summit than to the one anterior to it. Of the ribs, 16 occur upon all the whorls. The intersections of the ribs and spiral cords form strong, compressed tubercles, the long axes of which coincide with the spiral sculpture
. The spaces between the cords and ribs are well rounded, strongly impressed pits. The median cord on the first four whorls is a little stronger than the other two. On the penultimate whorl a slender, spiral cord makes its appearance, between the median and the supraperipheral cord, which on the last turn, immediately behind the aperture
, attains a strength equal to that of the spiral cord at the summit. The entire surface of the spire is marked by numerous, very fine, incremental lines. The periphery of the body whorl
is marked by a deep channel across which the axial ribs extend feebly. The base of the body whorl is well rounded. It is marked by four strong spiral keels, which are subequally spaced and grow somewhat weaker successively from the peripheral to the umbilical area. Immediately anterior to the last of these spiral keels there is a single, slender, raised spiral thread. The spaces between the spiral keels are crossed by slender continuations of the axial ribs and very fine lines of growth. The aperture is oval. The inner lip
is oblique, strong, slightly reflected upon and adnate to the base. It is provided
with a moderately strong fold at its insertion. The parietal wall is glazed with a thin 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 white shell moderately large measuring 3.2 mm. It is elongate-conic, with decidedly channeled sutures. The nuclear whorlWhorl
A whorl is a type of spiral or circular pattern.Other meanings of whorl include:* Whorl , used to describe the attachment of sepals, petals, leaves, or branches at a single point...
s number at least 2, forming a depressed helicoid 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...
, which is obliquely, almost one-half immersed in the first of the succeeding turns. The six post-nuclear whorls are moderately rounded. They are marked by strong, decidedly retractive, axial ribs and, on the first four turns, by three spiral cords which equal the ribs in strength; the middle one of these three cords is a little nearer that at the summit than to the one anterior to it. Of the ribs, 16 occur upon all the whorls. The intersections of the ribs and spiral cords form strong, compressed tubercles, the long axes of which coincide with the spiral 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...
. The spaces between the cords and ribs are well rounded, strongly impressed pits. The median cord on the first four whorls is a little stronger than the other two. On the penultimate whorl a slender, spiral cord makes its appearance, between the median and the supraperipheral cord, which on the last turn, immediately behind 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....
, attains a strength equal to that of the spiral cord at the summit. The entire surface of the spire is marked by numerous, very fine, incremental lines. 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 deep channel across which the axial ribs extend feebly. The base of the body whorl is well rounded. It is marked by four strong spiral keels, which are subequally spaced and grow somewhat weaker successively from the peripheral to the umbilical area. Immediately anterior to the last of these spiral keels there is a single, slender, raised spiral thread. The spaces between the spiral keels are crossed by slender continuations of the axial ribs and very fine lines of growth. The aperture is oval. The inner 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 oblique, strong, slightly reflected upon and adnate to the base. It is provided
with a moderately strong fold at its insertion. The parietal wall is glazed with a thin callus.