Odostomia excisa
Encyclopedia
Odostomia excisa is a species
of sea snail
, a marine
gastropod mollusk in the family
Pyramidellidae
, the pyrams and their allies.
are decollated. The six post-nuclear whorls are well rounded, appressed at the summit. They are marked by four equally strong but not equally spaced, incised, spiral lines between the sutures. The fourth of these is immediately above the periphery, while the first is as far below the summit as the third is posterior to the fourth. The second line divides the space between the first and third into equal halves, which are about one and a half times as wide as the spaces included between the third and fourth incised spiral. In addition to the spiral sculpture the whorls are crossed by numerous, fine, decidedly retractive, incremental lines. The periphery of the body whorl
is somewhat inflated, well rounded. The base of the shell is moderately long and moderately rounded, crossed
by 8 strongly incised, equal, spiral lines, which are a little stronger than those occurring on the spire
. These lines become exceedingly
closely spaced between the periphery and the umbilical area. The axial sculpture on the base is of the same character and strength as that appearing on the spire. All of the incised, spiral lines on base and spire are crossed by very slender, axial threads, which lend these channels a somewhat pitted appearance. The sutures are well impressed. The aperture
is moderately large, oval, and effuse anteriorly. The posterior angle is
acute. The outer lip
is thin, showing the external sculpture within. The inner lip oblique, moderately long, somewhat reflected, and re-enforced for the greater part of its length by the attenuated base, provided with an oblique 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 yellowish-white shell is moderately large and measures 3.9 mm. It is elongate-ovate. 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 decollated. The six post-nuclear whorls are well rounded, appressed at the summit. They are marked by four equally strong but not equally spaced, incised, spiral lines between the sutures. The fourth of these is immediately above the periphery, while the first is as far below the summit as the third is posterior to the fourth. The second line divides the space between the first and third into equal halves, which are about one and a half times as wide as the spaces included between the third and fourth incised spiral. In addition to the spiral sculpture the whorls are crossed by numerous, fine, decidedly retractive, 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 somewhat inflated, well rounded. The base of the shell is moderately long and moderately rounded, crossed
by 8 strongly incised, equal, spiral lines, which are a little stronger than those occurring 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...
. These lines become exceedingly
closely spaced between the periphery and the umbilical area. The axial sculpture on the base is of the same character and strength as that appearing on the spire. All of the incised, spiral lines on base and spire are crossed by very slender, axial threads, which lend these channels a somewhat pitted appearance. The sutures are well impressed. 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 moderately large, oval, and effuse anteriorly. 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 within. The inner lip oblique, moderately long, somewhat reflected, and re-enforced for the greater part of its length by the attenuated base, provided with an oblique fold at its insertion. The parietal wall is glazed with a thin callus.