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A rounded elevation of the surface of the tympanic membrane.
(invertebrate zoology)
A prominence above the hinge of a bivalve mollusk shell.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



the iron central boss of a shield, which protected the warrior’s hand. Under the hemispherical or conical umbo was a crosspiece by which the shield was held. Shields with umbones were widely used in ancient Greece and Rome and in medieval Europe and Rus’.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
It is usually developed in the umbonal region and in the rib interspaces (Fig.
Concha delgada y alargada, subrectangular; el lado anterior mas largo alcanza casi los dos tercios de la longitud total y tiene el borde redondeado, el borde dorsal anterior es recto y el posterior oblicuo forma un angulo con el borde posterior cuadrado y reflejado hacia la derecha,el cual queda abierto; la region umbonal es algo inflada y los picos pequenos son opistogirados, una suave area radial deprimida baja desde la region umbonal hasta el borde inferior de cada valva; solamente se observan finas lineas de crecimiento, mas notorias cerca de los bordes inferiores de las valvas; la charnela presenta dos dientes cardinales en cada valva; el periostraco es pardo claro, liso y brillante; el seno paleal es amplio, profundo y elevado dorsalmente y los bordes de las valvas lisos.
The umbonal cavity is shallow and a proeminent keel (k) arises from this region toward the posterior region of the shell.
Nevertheless, the presence of at least a very clear cardinal tooth and lateral teeth and the absence of umbonal sculpture make the adscription of theses shells to this genus difficult.
Hingeline straight; posterior margin strongly convex; anterior margin short, concave ventral to beaks becoming flatly convex before curving into broadly convex ventral margin; distinct, fairly deep sulcus radiating from umbonal area having a rounded fold within it in most specimens; surface ornament of numerous narrow, comarginal, erect lamellae which continue across sulcus and fold; hinge and internal features not observed.
Subsequent manipulations and observations of the thin cross-sections of whole valve were accomplished in the same manner as those for the shell's umbonal region, as described in the previous section.
Concha oval fragil subnacarada, algo inflada en la region umbonal, con dos lomos radiales que se proyectan desde el pico hasta el borde posterior truncado; charnela con ligamento opistodetico, largo y prominente, los dientes son aguzados, 17 a 19 anteriores y 25 a 27 posteriores; el seno paleal es profundo.
Subequally biconvex transverse shell with maximum width slightly anterior to the hinge line or at the hinge line, about 50-60% as thick as long; with a strong ventral sulcus and dorsal median fold originating at the umbonal area and occupying about 40% of maximum shell width; radial ornament with a single rib in a sulcus, two ribs on a dorsal fold and 4-7 on valve flanks; ventral median rib of equal size with ribs on valve flanks; ventral beak erect; delthyrial plates merged anterior to the elongate, submesothyrid pedicle foramen.
Most veligers were umbonal veligers and pediveligers from August 2008 to January 2009, umbonal veligers in February 2009, and straight-hinged veligers in March 2009.
Its locations were rather constant, at the opposite side of the umbonal area for the 3 size groups and prey groups considered, with no differences between both valves (see Fig.