The ventral valve is usually the larger, and in many genera, such as Terebratula and Rhynchonella, has a prominent beak or umbo, with a circular or otherwise shaped foramen at or near its extremity, partly bounded by one or two plates, termed a deltidium.
Except in a few aberrant types, which are mentioned below, the mouth is surrounded by a much developed lip like a funnel directed downwards, and is armed with a horny beak not unlike that of a cuttle-fish.
Owing to this joint the whole upper beak can be moved up and down with extra facility, according to the shoving forwards or backwards of the palato-pterygo-quadrate apparatus which moves sledge - like upon the cranial basis.
In bugs and aphids (Hemiptera), the fused second maxillae form a jointed grooved beak or rostrum (fig.
The beak is large, strong and sharp-edged, the upper mandible terminating in a large hook; the wings are narrow and very long; the feet have no hind toe, and the three anterior toes are completely webbed.
In coloration it bears some resemblance to a chaffinch, but its much larger size and enormous beak make it easily recognizable, while on closer inspection the singular bull-hook form of some of its wing-feathers will be found to be very remarkable.
The old fable of this bird inserting its beak into a reed or plunging it into the ground, and so causing the booming sound with which its name will be always associated, is also exploded, and nowadays indeed so few people in Britain have ever heard its loud and awful voice, which seems to be uttered only in the breeding-season, and is therefore unknown in a country where it no longer breeds, that incredulity as to its booming at all has in some quarters succeeded the old belief in this as in other reputed peculiarites of the species.
A family of predaceous bugs that attack other insects and suck their juices; the beak is short, and carried under the head in a hooklike curve, not - as in the preceding families - lying close against the breast.
The beak is hard, strong and deeply notched, the nostrils are prominent, and the gape is furnished with twelve long hairs on each side.
The beak is made up of horny elements, like the labial teeth, fused together; its edge, when sufficiently magnified, is seen to be denticulate, each denticle representing the cusp of a single tooth.