Alvania tarsodes

Alvania tarsodes
Shell of Alvania tarsodes (specimen at the Natural History Museum, Rotterdam)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Gastropoda
Subclass:	Caenogastropoda
Order:	Littorinimorpha
Superfamily:	Rissooidea
Family:	Rissoidae
Genus:	Alvania
Species:	A. tarsodes
Binomial name
Alvania tarsodes (Watson, 1886)
Synonyms
Rissoa (Alvania) tarsodesR. B. Watson, 1886 Rissoa tarsodesR. B. Watson, 1886

Alvania tarsodes is a species of minute sea snail, a marine gastropod mollusk or micromollusk in the family Rissoidae. ^[1]

Description

The length of the shell attains 1.8 mm.

(Original description) The shell is ovate to oblong, conical and blunt tipped. It is white, rather finely reticulated, with a round aperture, and a remotely varixed thin-edged lip.

Sculpture  : Longitudinals — there are about 20 sharpish rounded ribs, which, strong at the suture, die out rather suddenly toward the edge of the base. The last, which is rather remote from the lip-edge, is a broad strong varix, the shallow interstices are fully broader than the ribs.

Spirals — there are about eight sharpish threads, much like the ribs. The first is rather remote from the suture. The last two, which are in the middle of the base, are feeble, the shallow interstices are fully broader than the spirals.

The colour of the trnaslucent shell is dull white.

The spire is rather high and conical. The apex blunt, the first two whorls being rather depressedly globose, and quite smooth. The shell contains 5 convex whorls, of regular increase. The suture is impressed, and very slightly oblique. The aperture is sub-oval, a little oblique to the axis and bluntly pointed above. The outer lip is expanded, with a thin-edged, remotely varixed lip. Its sweep is a very regular curve, and its front line level. The inner lip is not thick, but distinct on the body. On the columella it is narrow, sharp, and prominent, with a minute umbilical channel behind it. ^[2]

Distribution

This species occurs in the Atlantic Ocean off the Azores.

References

1. Alvania tarsodes (Watson, 1886) . Gofas, S. (2009). Alvania tarsodes (Watson, 1886). In: Bouchet, P.; Gofas, S.; Rosenberg, G. World Marine Mollusca database. Accessed through the World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=141248 on 9 August 2010 .
2. • Watson, R. B. (1886). Report on the Scaphopoda and Gasteropoda collected by H.M.S. Challenger during the years 1873-76. Report on the Scientific Results of the Voyage of H.M.S. Challenger during the years 1873–76. Zoology 15 (part 42): 1-756, pls 1-50

External links

• 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