Miralda mariella
Encyclopedia
Miralda mariella is a species
of sea snail
, a marine
gastropod mollusk in the family
Pyramidellidae
, the pyrams and their allies.
and deeply channeled sutures. The whorls
of the protoconch
are almost completely immersed in the first whorl of the teleoconch. Only half of the last volution projects above it. The four whorls of the teleoconch are flattened. They are marked by strong, very obliquely backward-slanting axial ribs, which are thickened at the summits and constricted a little below the summit, which renders the top of each rib beaded. Anteriorly the ribs are terminated by the posterior margin of the peripheral sulcus; here the ribs expand somewhat and almost fuse, and this expansion gives them a subnodulose effect at this point. The intercostal spaces are smooth, about as wide as the axial ribs, decidedly depressed in the middle—that is, between the bead at the summit and the nodules at the periphery. The periphery of the body whorl
is deeply sulcate. The base of the shell is well rounded. It is marked by about nine spiral lirations, the posterior one of which is decidedly wider than the rest. The depressed spaces between the lirations are marked by fine axiaf threads. Both the spiral lirations and the spaces between them gradually diminish in width from the periphery to the umbilical area. The aperture
is suboval The posterior angle is acute. The columella is strongly oblique, somewhat revolute, re-enforced by the somewhat attenuated base and provided with a fairly strong oblique fold near its insertion. The parietal wall is covered by a thick callus, which gives the periostracum
a continuous appearance. On the body whorl the first basal keel appears above the sutures, which is therefore not channeled like the sutures of the preceding whorls.
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 small, milk-white shell grows to a length of 2.0 mm. It is umbilicated, regularly conic with an obliquely truncated apexApex (mollusc)
Apex is an anatomical term for the tip of the mollusc shell of a gastropod, scaphopod, or cephalopod mollusc.-Gastropods:The word "apex" is most often used to mean the tip of the spire of the shell of a gastropod...
and deeply channeled sutures. The whorls
Whorl (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...
of the protoconch
Protoconch
A protoconch is an embryonic or larval shell of some classes of molluscs, e.g., the initial chamber of an ammonite or the larval shell of a gastropod...
are almost completely immersed in the first whorl of the teleoconch. Only half of the last volution projects above it. The four whorls of the teleoconch are flattened. They are marked by strong, very obliquely backward-slanting axial ribs, which are thickened at the summits and constricted a little below the summit, which renders the top of each rib beaded. Anteriorly the ribs are terminated by the posterior margin of the peripheral sulcus; here the ribs expand somewhat and almost fuse, and this expansion gives them a subnodulose effect at this point. The intercostal spaces are smooth, about as wide as the axial ribs, decidedly depressed in the middle—that is, between the bead at the summit and the nodules at the periphery. 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 deeply sulcate. The base of the shell is well rounded. It is marked by about nine spiral lirations, the posterior one of which is decidedly wider than the rest. The depressed spaces between the lirations are marked by fine axiaf threads. Both the spiral lirations and the spaces between them gradually diminish in width from the periphery to the umbilical area. 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 posterior angle is acute. The columella is strongly oblique, somewhat revolute, re-enforced by the somewhat attenuated base and provided with a fairly strong oblique fold near its insertion. The parietal wall is covered by a thick callus, which gives the periostracum
Periostracum
The periostracum is a thin organic coating or "skin" which is the outermost layer of the shell of many shelled animals, including mollusks and brachiopods. Among mollusks it is primarily seen in snails and clams, i.e. in bivalves and gastropods, but it is also found in cephalopods such as the...
a continuous appearance. On the body whorl the first basal keel appears above the sutures, which is therefore not channeled like the sutures of the preceding whorls.