VARIOUS FORMS OF BILLS. 25 
convenieut incidental terms in general descriptions. Various other lesser 
terms, expressing special modifications, as lamellirostral, acutirostral, etc., 
are employed; but all are best used, now, as common, not as proper names, 
simply descriptive of 
§ 47. Orser Forms. A bill is called Jong, when notably longer than the 
head proper; shoré, when notably shorter; medium, in neither of these con- 
ditions. It is compressed, when higher than wide, at the base at least, and 
generally for some portion of its length; depressed, when wider than high ; 
terete, under neither of these conditions. It is recurved, when curved up- 
ward; decurved, when curved downward; bent, when the variation in either 
direction is at an angle ; straight, when not out of line with axis of the head. 
A bill is obtuse (said chiefly of the paragnathous sort) when it rapidly 
comes to an end that therefore is not fine; or when the end is knobby; it is 
acute when it runs to a sharp point; acwminate, when equally sharp and slen- 
derer; attenuate, when still slenderer; subulate (awl-shaped), when slen- 
derer still; acicular (needle-shaped), when slenderest possible, as in some 
humming-birds. <A bill is arched, vaulted, turgid, tuwmid, inflated, etc., 
when its outlines, both crosswise and lengthwise, are notably more or less 
convex; and contracted, when some, or the principal, outlines are concave 
(said chiefly of depressions about the base of the upper mandible, or of con- 
eavity along the sides of both mandibles). A bill is hamulate (hooked) or 
unguiculate (clawed), when strongly epignathous, as in rapacious birds, 
3 where the upper mandible is like the talon of a carnivorous beast; it is den- 
tate, when toothed (§ 46), as in a falcon; if there are a number of sim- 
ilar “teeth,” it is serrate (like a saw); it is cultrate (knife-like) when ex- 
tremely compressed and sharp-edged, as in the auk, skimmer; if much 
‘curved as well as cultrate, it is fulcate (scythe-shaped) ; and each mandible 
3 may be oppositely faleate, as in the cross-bill. A bill much flattened and 
} widened at the end (rare) is spatulate; examples: spoonbill, shoveller duck. 
One is called lamellate, when it has a series of plates or processes just inside 
the edges of the mandibles; as in all the duck order, and in a few petrels ; 
the design is to furnish a sifter or strainer of water, just what is effected in the 
whale, by the “bone” in its mouth. Finally, the far end of the bill, of what- 
ever shape, is called the éép or apex (fig. 5, n); the near end, joined to the 
rest of the skull, the dase; the rest is the continuity. Some other features 
of the bill as a whole are best treated under separate head of 
§ 48. THE COVERING OF THE BILL. (a.) In the great majority of birds, 
including nearly all perchers, many walkers and some swimmers, the sheath- 
ing of the mandibles is wholly hard, horny or corneous; it is integument 
modified much as in the case of the nails or claws of beasts. In nearly all 
waders and most swimmers, the sheath becomes, wholly or partly, softer, and 
is of a dense, leathery texture. But some swimmers, as among the auks, 
furnish bills as hard-covered as any, while some perchers have it partly quite 
soft, so that no unexceptional rule can be laid down; and, moreover, 
the gradations from one extreme to the other are insensible. Probably, 
KEY TO N. A. BIRDS. 4 
ee Pee ee ee 
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. 
