UMBONIUM SHELLS KNOWLEDGE BASE

Umbonium Shells

Umbonium, often referred to as "button top shells," represents a genus of sea snails, which are marine gastropod mollusks belonging to the family Trochidae, commonly known as top snails.

The shells of species in this genus are characterized by their low-spired, button-like shape. The orbicular shell is depressed, imperforate, and exhibits a polished, porcelain-like surface with a very thin, pearly layer on the inside. The whorls are flattened on top, appearing bright and either smooth or marked with spiral grooves. The small, transverse aperture is broader than it is tall. The outer lip of the shell is thin and sharp, while the inner lip is rounded, terminating in a simple point. Often, the shell's umbilicus is entirely obscured by a thick, smooth callus.

The creature features a pronounced lateral fringe on the foot, sporting three filaments per side. At the tentacles' base on the right, there's a protruding fleshy lobe. The right tentacle itself is unattached, with a compressed eye-peduncle that has a basic eye. In contrast, the left eye-peduncle is cylindrical, equipped with a clear eye and a frontal lobe that is folded and fringed along its edge. Its operculum is hard, circular, and displays a multispiral pattern.

Umboniums can be found throughout the Indo-Pacific region, extending from the Indian Ocean to the Sea of Japan and reaching as far south as the Australian coast.

Scientific classification

Domain: Eukaryota

Kingdom: Animalia

Phylum: Mollusca

Class: Gastropoda

Subclass: Vetigastropoda

Order: Trochida

Superfamily: Trochoidea

Family: Trochidae

Genus: Umbonium

Link, 1807

(REF: Link J. H. F. (1807). Beschr. Nat. Samml. Univ. Rostock 3)(REF: Bouchet, P. (2012). Umbonium Link, 1807. Accessed through: World Register of Marine Species)(REF: Tryon (1889), Manual of Conchology XI, Academy of Natural Sciences, Philadelphia)(REF:Proceedings of the Zoological Society of London pt. 21-23 (1853-1855)

The size of the shell varies between 1/4 to 1 inch . The heavy, solid shell has a depressed shape. Its spireis low-conoidal, the periphery rounded. The color pattern is whitish or light yellow, closely tessellated all over with blackish-olive or reddish-brown squarish spots. The tessellated color-markings sometimes form subcontinuous oblique bands. The surface is shining and polished, with strong spiral grooves above, generally 4 to 6 on the body whorl. The sutures are narrowly impressed, with a rather wide margin below them, which often shows a slight tendency to be tuberculate. The base of the shell is smooth, tessellated around the irregularly convex, flesh-colored central callus. The shell contains six whorls, the last a little concave above, convex beneath. The subquadrate aperture is pearly inside. The circular callus is heaviest in front of the aperture and behind the columellar lip.

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