''Thesbia nana'' is a
species of
sea snail
Sea snail is a common name for slow-moving marine gastropod molluscs, usually with visible external shells, such as whelk or abalone. They share the taxonomic class Gastropoda with slugs, which are distinguished from snails primarily by the ...
, a marine
gastropod
The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda ().
This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...
mollusk in the
family Raphitomidae
Raphitomidae is a family of small to medium-sized sea snails, marine gastropod mollusks in the superfamily Conoidea.Bouchet P. & Rocroi J.-P. (Ed.) (2005). "Classification and nomenclator of gastropod families". '' Malacologia'' 47(1-2). . 3 ...
.
Description
The length of the shell attains 12 mm.
The body of the snail is milk-white, all but the gills and liver, which are light brown. The tentacles are cylindrical, rather short. The eyes are proportionally large, placed on the tentacles, close to their outer bases. The foot nis arrow and thin.
The shell is spindle-shaped, thin, semitransparent, and glossy. The
sculpture shows numerous fine and narrow spiral impressed hues, of which there are about a dozen on the penultimate whorl. They are closely and regularly punctured, so as to form rows of circular dots. The top
whorls are very closely and microscopically corrugated in the same direction. The colour is uniform milk-white. There is no epidermis perceptible . The
spire is tapering. The
apex is abruptly twisted. The shell contains 4½ to 5½
whorl
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 ...
s, convex and evenly rounded, rather suddenly enlarging; the last occupies about three-fifths of the shell. The suture is deep, somewhat oblique. The
aperture is irregularly oblong, acute-angled above. Its length (including the
siphonal canal
The siphonal canal is an anatomical feature of the shells of certain groups of sea snails within the clade Neogastropoda. Some sea marine gastropods have a soft tubular anterior extension of the mantle called a siphon through which water is ...
) is two-fifths of the shel. The siphonal canal is rather broad, inclining a little (but not abruptly) to the left, and ending in a slight and obliquely curved notch. The outer
lip is flexuous, retreating at the upper part, but without exhibiting any fissure or notch . It folds inwards rather than outwards. The
edge is sharp and thin. Inside it isquite smooth. The inner lip is slight, narrow, and even. The
columella is flexuous. The fold is obscure. There is no
operculum.
Jeffreys, 1867: British Conchology: or, an Account of the Mollusca Which Now Inhabit the British Isles and the Surrounding Seas
Distribution
This species occurs in the Atlantic Ocean from Eastern Canada to Norway and the Barentz Sea
The Barents Sea ( , also ; no, Barentshavet, ; russian: Баренцево море, Barentsevo More) is a marginal sea of the Arctic Ocean, located off the northern coasts of Norway and Russia and divided between Norwegian and Russian territo ...
.
References
* McAndrew R. & Forbes E. (1847). ''Notices of new or rare British animals observed during cruises in 1845 and 1846''. Annals and Magazine of Natural History 19: 96-98, pl. 9
* Gofas, S.; Le Renard, J.; Bouchet, P. (2001). Mollusca. in: Costello, M.J. et al. (eds), European Register of Marine Species: a check-list of the marine species in Europe and a bibliography of guides to their identification. Patrimoines Naturels. 50: 180-213
* Nekhaev, I.O. 2014. Marine shell-bearing gastropoda of Murman (Barentz Sea) - an annotated checklist.
External links
Lovén, S. L. (1846). Index Molluscorum litora Scandinaviae occidentalia habitantium. Öfversigt af Kongliga Vetenskaps Akademiens Förhandlingar. (1846): 134-160, 182-204.
Dyntaxa. (2013). Swedish Taxonomic Database
Biolib.cz: ''Thesbia nana''
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{{DEFAULTSORT:Thesbia Nana
nana
Gastropods described in 1846