Odostomia exarata
Encyclopedia
Odostomia exarata is a species
of sea snail
, a marine
gastropod mollusk in the family
Pyramidellidae
, the pyrams and their allies.
are obliquely immersed, only the tilted edge of the last volution is visible. The five post-nuclear whorls are marked by two spiral keels which divide the space between the sutures into three equal parts. The posterior of these keels shows weak crenulation. The periphery of the body whorl
is marked by a third keel which is almost as strong as those on the spire. A fourth keel considerably less strong occupies the middle of the base. The rounded spaces between the keels are marked by feeble lines of growth. The aperture
is irregularly oval. The posterior angle is obtuse. The outer lip
is angulated by the keels. The columella is strong, reflected and provided with a weak fold at insertion. The parietal wall is covered with a thin callus.
. The type specimen was found off Mazatlán
, Mexico.
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 elongate-ovate shell is white. 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 obliquely immersed, only the tilted edge of the last volution is visible. The five post-nuclear whorls are marked by two spiral keels which divide the space between the sutures into three equal parts. The posterior of these keels shows weak crenulation. 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 third keel which is almost as strong as those on the spire. A fourth keel considerably less strong occupies the middle of the base. The rounded spaces between the keels are marked by feeble lines of growth. 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 irregularly oval. The posterior angle 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 angulated by the keels. The columella is strong, reflected and provided with a weak fold at insertion. The parietal wall is covered with a thin callus.
Distribution
This species occurs in the Pacific Ocean off the Galapagos IslandsGalápagos Islands
The Galápagos Islands are an archipelago of volcanic islands distributed around the equator in the Pacific Ocean, west of continental Ecuador, of which they are a part.The Galápagos Islands and its surrounding waters form an Ecuadorian province, a national park, and a...
. The type specimen was found off Mazatlán
Mazatlán
Mazatlán is a city in the Mexican state of Sinaloa; the surrounding municipio for which the city serves as the municipal seat is Mazatlán Municipality. It is located at on the Pacific coast, across from the southernmost tip of the Baja California peninsula.Mazatlán is a Nahuatl word meaning...
, Mexico.