Alvania aequisculpta

Alvania aequisculpta
Shell of Alvania aequisculpta
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Gastropoda
Subclass:	Caenogastropoda
Order:	Littorinimorpha
Superfamily:	Rissooidea
Family:	Rissoidae
Genus:	Alvania
Species:	A. aequisculpta
Binomial name
Alvania aequisculpta Keep, 1887
Synonyms
Alvinia aequisculpta(Keep, 1887) Manzonia aequisculpta(Keep, 1887) Rissoina aequisculpta(Keep, 1887)

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

Taxonomy

This and other Western American species were attributed to AlviniaMonterosato, 1884, following Keen (1971); nevertheless it is not proved to be more related to the Mediterranean type species Alvania weinkauffi Weinkauff, 1868 than to other Alvania s.l. and is therefore retained in Alvania.

Description

The length of the shell varies between 5 mm and 10 mm.

(Original description) The minute shell is slender, and coarsely cancellated. The spire is five-whorled, and the aperture is circular and entire. Its color is white, and its length is only one-eighth of an inch. ^[2]

The very elongate-conic shell is light yellow. The protoconch contains two, moderately well rounded whorls. They are marked by six spiral threads, which are about as wide as the spaces that separate them, and numerous slender, closely spaced, axial threads, which are about one-fourth as strong as the spiral threads between which they occur, giving the entire surface a finely reticulated appearance. The whorls of the teleoconch are appressed at the summit. They show a sloping shoulder which extends over the posterior fourth between the sutures, marked by strong, slightly retractive, axial ribs which are about one-fourth as wide as the spaces that separate them. Of these ribs, 14 occur upon the first, 16 upon the second, and 18 upon the penultimate whorl. In addition to the axial ribs, the whorls are marked between the sutures by three strong, spiral cords which are almost as strong as the ribs and divide the spaces between the sutures into four almost equal portions. The intersections of the spiral cords and the axial ribs form strong tubercles, while the spaces enclosed between them are well impressed, rectangular pits, having their long axes parallel with the spiral sculpture. The suture is strongly constricted. The periphery of the body whorl is marked by a spiral sulcus equal to that which separates the supraperipheral spiral cord from its posterior neighbor and, like it, is crossed by the continuations of the axial ribs, which extend over the first two basal spiral cords and render them tuberculate. The base of the shell is well rounded, rather short, produced anteriorly, and marked by three strong, sublamellar, spiral cords which are about one-third as wide as the spaces that separate them. The aperture is very oblique, twisted and ovate. The posterior angle is obtuse. The outer lip is thickened at the edge within the lip, re-enforced behind the edge by a strong varix. The inner lip is very stout, strongly curved, and appressed to the base. The parietal wall is covered with a very thick callus, which renders the peritreme complete. ^[3]

Distribution

This marine species occurs off Southeast USA; Bahamas; Cuba; Colombia.

References

1. MolluscaBase eds. (2024). MolluscaBase. Alvania aequisculpta Keep, 1887. Accessed through: World Register of Marine Species at: https://www.marinespecies.org/aphia.php?p=taxdetails&id=593627 on 2024-01-16
2. Josiah Keep (1887), West Coast Shells
3. Dall, W. H. (1927). Small shells from dredgings off the southeast coast of the United states by the United States Fisheries Steamer "Albatross", in 1885 and 1886. Proceedings of the United States National Museum. 70(2667): 1-134 This article incorporates text from this source, which is in the public domain .

• Keep, J. (1888) West Coast Shells. Samuel Carson & Co., San Francisco, 230 pp.
• Abbott, R. T. (1974). American seashells. The marine Mollusca of the Atlantic and Pacific coast of North America. ed. 2. Van Nostrand, New York. 663 pp., 24 pls. [October 1974].

External links

• Bartsch, P. (1911). The Recent and fossil mollusks of the genus Alvania from the west coast of America. Proceedings of the United States National Museum. 41(1863): 333-362
• West Coast Shells, p. 65 ; Proc. U. S. Nat. Mus., vol. 41, p. 358, pi. 32, fig. 7