Pyrgulina lecta
Encyclopedia
Pyrgulina alveata is a species
of very small sea snail
, a pyramidellid
gastropod micromollusk
. This genus is currently placed in the subfamily Chrysallidinae
of the family
Pyramidellidae
.
moderately' large, deeply obliquely immersed in the first of the succeeding whorls, only the last half turn of the last volution is visible from the side.The six post-nuclear whorls are rather high between the sutures, somewhat flattened, the summit of the succeeding whorls falls a little anterior to the periphery of the preceding one. This gives the whorls a constricted appearance at the suture. The whorls are ornamented by strong sublamellar axial ribs, which are thickened and cuspid at the summit. Fourteen of these ribs occur upon the first, sixteen upon the third, and twenty upon the penultimate whorl. The intercostal spaces are broad and rounded, fully three times the width of the ribs, crossed by narrow, incised spiral lines, which are about one-fourth as wide as the space enclosed between them. Twelve of these lines occur between the sutures upon the fourth and penultimate whorls. The periphery and the base of the body whorl
are well rounded, the latter attenuated. They are marked like the space between the sutures by the prominent continuations of the axial ribs and ten incised strong, spiral lines. The aperture
is suboval. The columella is short, curved, re-enforced by the attenuated base, provided with a strong, oblique fold near its insertion. The parietal wall is covered by a moderately thick callus, which extends over the umbilical area.
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 very small sea snail
Snail
Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...
, a pyramidellid
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....
gastropod micromollusk
Micromollusk
A micromollusk is a descriptive term for a shelled mollusk which is extremely small, even at full adult size. The word is usually, but not exclusively, applied to marine mollusks, although in addition, numerous species of land snails and freshwater mollusks also reach adult size at very small...
. This genus is currently placed in the subfamily Chrysallidinae
Chrysallidinae
Chrysallidinae is a taxonomic group of very small sea snails in the family Pyramidellidae.- Taxonomy :Chrysallidinae has been one of eleven recognized subfamilies of the gastropod family Pyramidellidae...
of 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....
.
Description
The elongate-ovate shell is turrited, shouldered, sutures crenulated, shining, hyaline to milk-white. It measures 3.4 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...
moderately' large, deeply obliquely immersed in the first of the succeeding whorls, only the last half turn of the last volution is visible from the side.The six post-nuclear whorls are rather high between the sutures, somewhat flattened, the summit of the succeeding whorls falls a little anterior to the periphery of the preceding one. This gives the whorls a constricted appearance at the suture. The whorls are ornamented by strong sublamellar axial ribs, which are thickened and cuspid at the summit. Fourteen of these ribs occur upon the first, sixteen upon the third, and twenty upon the penultimate whorl. The intercostal spaces are broad and rounded, fully three times the width of the ribs, crossed by narrow, incised spiral lines, which are about one-fourth as wide as the space enclosed between them. Twelve of these lines occur between the sutures upon the fourth and penultimate whorls. The periphery and the base 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...
are well rounded, the latter attenuated. They are marked like the space between the sutures by the prominent continuations of the axial ribs and ten incised strong, 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 suboval. The columella is short, curved, re-enforced by the attenuated base, provided with a strong, oblique fold near its insertion. The parietal wall is covered by a moderately thick callus, which extends over the umbilical area.