A genus of brachiopodous bivalves, distinguished by the valves being nearly equal, and the umbones not separated by an intermediate area.
The general form, the thickened hinge reaching across the cavity of the valve and the terminal umbones serve to distinguish this genus from Cardita, to which, however, it is nearly allied.
When the umbones of a bivalve shell are placed at or near the extremity, as in Mytilus, fig.
A shell is said to be transverse, when its width is greater than its length, that is, when it is longer from one side to the other than from the umbones to the ventral margins.
The small, equal, equilateral valves are cemented into, so as to form part of, a large tube; the umbones are slightly prominent outside.
The above description of the genus Solen, is framed so as to admit only those species which are commonly called Razor Shells, with the umbones terminal, and the anterior muscular impression behind them.
Equivalve, globose, closed at the back; with a large, angular hiatus in front; hinge with a small curved tooth advancing from beneath the umbones in each valve.
The umboneswill be marked with the letter u, in Cytherea, fig.
When the umbonesare about central in respect to the posterior [pg418] and anterior margins, the shells are said to be /equilateral/.
The shell is ventricose, is closed or gapes slightly posteriorly, and has prominent subcentral umbones and an external ligament.
The most prominent feature of this species is a depressed line upon either valve extending obliquely from the umbones to the posterior ventral margin, [pg443] causing, at the margin, a pucker or break in its even continuity.
The length of bivalve shells is measured from their anterior to their posterior ends, while the height indicates the greatest diameter between the umbones and the ventral margin.
It may be distinguished by a rib-like wave extending obliquely from the umbones to the ventral margin of the shell.
The right and left valves may be distinguished by remembering that the siphons are always posterior, and that the umbones usually point forward.
Similarly placed back of the umbones is sometimes a more or less clearly defined space called the /escutcheon/.
Shell with sub-equal valves and prominent umbones more or less spirally coiled; ligament external.
Hinge pliodont, that is to say, it has numerous teeth on either side of the umbones and the teeth are perpendicular to the edge.
Siphons present; external gill-plate smaller than the internal; umbones not prominent.
Two short siphons, shell with prominent umbones and internal ligament.
Shell transverse; umbones remote; valves gaping in the middle of the ventral margin.
Noae; from which it differs in sculpture, colour, and in the umbones being less remote from each other.
The shell is oval and thick, with the umbones prominent and turned towards the posterior side, and the ligament is strong and prominent.
The shell, also, is more oblong in form, and much swollen near the anterior end; and the umbones are not so pointed.
The shell is regular, or nearly so, and the valves, which are equal, are ornamented with prominent rays that run from the umbones to the margin.
In this group the shell is more or less wedge-shaped, with equal valves, and the umbones are quite at the anterior end, while it is blunted and gaping at the other end.
The heart-shaped shell is thick and strong, and is swollen out in such a manner that the umbones are wide apart.
The umbones are at the anterior end of the shell, which end is usually very narrow and pointed, while the posterior is broad and rounded.
In all these the points of the umbones are invariably white.
Valves 5, approximate; scuta with their umbones in the middle of the occludent margin; carina rectangularly bent, extending up between the terga, with the basal end simply concave.
The umbones of these two latera are seated at their basal outer angles, so that the growth of the valves is towards each other and upwards.
The umbones of the two valves almost touch each other under the middle of the carina; main growth towards the infra-median latera and upwards; umbones projecting not above one fifth of the entire length of the valve.
Primordial valves very plain at the umbones of the lateral segments, but none are visible on the occludent segments; and this makes me believe that these two pieces are normally parts of a single valve; having only one specimen of P.
From the hollows on the under sides of the scuta, for the lodgment of the males; from the umbones of the scuta and of the carina being situated on the apices of these valves; and from all the characters of the mouth, S.
They are placed far distant from each other; their inner surfaces are triangular; their umbones point upwards; the rostral pair is smaller than the other two pair, which are of equal size.
Scuta nearly oval, with their umbones at the rostral angle.
The latter, in well preserved old specimens, may often be detected on the umbones of the scuta, terga, and carina, but not on the umbones of any other valves.
The umbones of the valves (together with the primordial valves) are nearly central, so that they are added to at their upper and lower ends; hence their manner of growth is considerably different from that of the valves in Lepas.
The pointed umbones are divergent, and internally under each, there is a large tooth.
The umbones of the compartments are remarkably prominent and sharp.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "umbones" in a variety of sentences. We hope that you will now be able to make sentences using this word.
