noun (plural umbones /ˌəmˈbōnēz/ or umbos)
2.1 Zoology The highest point of each valve of a bivalve shell.
- The new species is characterized by a transversely extended, strongly biconvex to globular shell with prominent umbones, relatively numerous costae and a notothyrial cavity supported dorsally by a short median ridge.
- Argonauta attaches the egg-mass to the umbo of the shell near the dorsal arms, not in the mantle cavity or posterior parts of the shell.
- Below the umbones, the shell margin is folded inward forming a deep lunula and gaping between both valves.
- (chiefly Zoology )Example sentences
- Cyzicus having elongate valves; umbo convex; dorsal margin straight; posterior margin slightly flared; growth bands widely spaced in umbonal region, more closely spaced elsewhere.
- The umbonal angle narrows while the shape remains mytiliform and the ‘lunule’ (byssal invagination) remains shallow.
- Hinge articulation either limited to overlapping shell margins on dorsal side of byssal invagination or consisting of a transposable tooth and socket developed on the umbonal septum.
- (chiefly Botany )Example sentences
- M. oreades has a white spore print, adnate, adnexed or even free gills usually white to pale tan in colour, a mid-sized bell-shaped cap but can later become umbonate as it ages.
- Other decorative British products of this period include ‘umbonate’ disc brooches.
- An umbonate colony is elevated more in the center of the colony than the rise across the surface of the colony.
Early 18th century: from Latin, 'shield boss'.
Words that rhyme with umboColombo, dumbo, gumbo, jumbo, mumbo-jumbo
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