''Lacuna'' is a
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
of
sea snails,
marine gastropod mollusk
Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is e ...
s in the
family
Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...
Littorinidae
The Littorinidae are a Taxonomy (biology), taxonomic family (biology), family of over 200 species of sea snails, marine (ocean), marine gastropod molluscs in the clade Littorinimorpha, commonly known as periwinkles and found worldwide.
Names
In ...
, the winkles or periwinkles.
Description
The spiral animal body is elongated. The mouth has a
proboscis
A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular mouthparts used for feeding and sucking. In vertebrates, a proboscis is an elong ...
with two thick lips and a spiral, filiform tongue. There are two slender, contractile tentacles with the eyes on small pedicels near their base. The foot is oval and somewhat broader behind.
The thin shell has an ovate-conical or subglobose shape and is covered with a delicate horny
periostracum. It has a short spire with convex
whorls
A whorl ( or ) is an individual circle, oval, volution or equivalent in a whorled pattern, which consists of a spiral or multiple concentric objects (including circles, ovals and arcs).
Whorls in nature
File:Photograph and axial plane floral ...
that are rapidly expanding. The last whorl is ventricose, i.e. inflated in the middle. The
apex
The apex is the highest point of something. The word may also refer to:
Arts and media Fictional entities
* Apex (comics), a teenaged super villainess in the Marvel Universe
* Ape-X, a super-intelligent ape in the Squadron Supreme universe
*Apex, ...
is rather obtuse. The oval or roundish
aperture
In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane.
An ...
is covered with a horny, spirally marked
operculum. The
peristome Peristome (from the Greek ''peri'', meaning 'around' or 'about', and ''stoma'', 'mouth') is an anatomical feature that surrounds an opening to an organ or structure. Some plants, fungi, and shelled gastropods have peristomes.
In mosses
In mosse ...
is incomplete behind. The
columella
Lucius Junius Moderatus Columella (; Arabic: , 4 – ) was a prominent writer on agriculture in the Roman Empire.
His ' in twelve volumes has been completely preserved and forms an important source on Roman agriculture, together with the wo ...
is flattened and forms with the peristome an elongated groove continued from the
umbilicus. This groove is bounded internally by the decurved margin of the pillar.
Species
The following species are recognised in the genus ''Lacuna'':
*''
Lacuna amaina''
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Lacuna carinifera''
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Lacuna cleicecabrale''
*''
Lacuna crassior''
*''
Lacuna decorata''
*''
Lacuna dialyta''
*''
Lacuna dutemplii''
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Lacuna globulosa''
*''
Lacuna grandis''
*''
Lacuna houdasi''
*''
Lacuna latifasciata''
*''
Lacuna lepidula''
*''
Lacuna lukinii''
*''
Lacuna macrostoma''
*''
Lacuna marmorata''
*''
Lacuna minor''
*''
Lacuna orientalis''
*''
Lacuna pallidula''
*''
Lacuna parva''
*''
Lacuna porrecta''
*''
Lacuna pulchella''
*''
Lacuna pumilio''
*''
Lacuna reflexa''
*''
Lacuna sigaretina''
*''
Lacuna smithii''
*''
Lacuna succinea''
*''
Lacuna sulcifera''
*''
Lacuna turgida''
*''
Lacuna turneri''
*''
Lacuna turrita''
*''
Lacuna uchidai''
*''
Lacuna unifasciata''
*''
Lacuna vaginata''
*''
Lacuna variegata''
*''
Lacuna vincta''
;Species brought into synonymy:
* ''Lacuna abyssicola'' Melvill & Standen, 1912: synonym of ''
Moelleriopsis poppei'' Engl, 2012
* ''Lacuna azonata'' Locard, 1886: synonym of ''
Megalomphalus azoneus'' (Brusina, 1865)
* ''Lacuna carinata'' Gould, 1848: synonym of
Lacuna vincta (Montagu, 1803)
* ''Lacuna cossmanni'' Locard, 1897 : synonym of ''
Benthobia tryonii'' Dall, 1889
* ''Lacuna macmurdensis'' Hedley, 1911 : synonym of ''
Trilirata macmurdensis'' (Hedley, 1911)
* ''Lacuna mediterranea'' Monterosato, 1869 : synonym of ''
Ersilia mediterranea'' (Monterosato, 1869)
* ''Lacuna neritoidea'' Gould, 1840 : synonym of ''Lacuna pallidula'' (da Costa, 1778)
* ''Lacuna notorcadensis'' Melvill & Standen, 1907:
synonym of ''
Laevilitorina wandelensis'' (Lamy, 1905)
* ''Lacuna pallidula'' var. ''patula'' Hanley in Thorpe, 1844: synonym of ''Lacuna pallidula'' (da Costa, 1778)
* ''Lacuna puteolus'' (Turton, 1819) : synonym of ''Lacuna parva'' (da Costa, 1778)
References
* Reid D. G. (1989). "The comparative morphology, phylogeny and evolution of the gastropod family Littorinidae". ''Philosophical Transactions of the Royal Society of London'', Series B 324: 1-110
External links
Miocene Gastropods and Biostratigraphy of the Kern River Area, California; United States Geological Survey Professional Paper 642
{{Taxonbar, from=Q6469078
Littorinidae