EXTERNAL PARTS OF BIRDS.—THE BILL. 101 
Four Classes, representing as many ways in which the two mandibles close upon each 
other at the end. 1. The epignathous (Gr. emi, epi, upon, yrados, gnathos, jaw) way, plan, or 
type, in which the upper mandible is longer than the under, and its tip is evidently bent down 
over the tip of the lower. 2. The hypognathous (Gr. ind, hupo, under), in which the lower 
mandible is longer than the other. 3. The paragnathous (Gr. rapa, para, at or by), in which 
both are of about equal length, and neither is evidently bent over the other. 4. The metagna- 
thous (Gr. pera, meta, with, beside, etc.), in which the points of the mandibles cross each 
other. The second and fourth of these are extremely rare; they are exemplified, respectively, 
by the skimmer and the cross-bill (genera Rhynchops and Loxia). The first is common, 
occurring throughout the birds of prey, the parrots, and among the petrels, gulls, ete., ete. 
The great majority of birds exhibit the third; and, among them, there is such evident grada- 
tion into epignathism, that it is necessary to restrict the latter to its complete development, 
exhibited in the intermaxillary bone divested of its horny sheath, which often, as among fly- 
catchers, ete., forms a little overhanging point, but does not constitute epignathism. These 
classes, it should be added, though always applicable, and very convenient in descriptions, are 
purely arbitrary, that is, they by no means correspond to any four large groups of birds ; but, 
on the contrary, usually only mark families and the subdivisions of families; and the four 
types may be seen in contiguous genera. The general shape of the bill has also furnished 
Other Classes, for many years used as a large basis for ornithological classification, even 
for the establishment of orders; but which the progress of the science has shown to be merely 
as convenient as, and only less arbitrary than, the foregoing. The principal of these are 
represented by the following types: A, among land birds. 1. The fisstrostral (Lat. fissus, 
cleft, and rostrum), or cleft, in which the bill is small, short, and with a very large gap run- 
ning down the side of the head; as in the swallow, chimney-swift, whippoorwill. 2. The 
tenuirostral (Lat. tenwis, slender), or slender, in which the bill is small, long, and with a short 
cleft ; as in the humming-bird, creeper, nuthatch. 3. The dentirostral (Lat. dens, a tooth), 
or toothed, in which, with a various general shape, there is present a nick, tooth, or evident 
lobe in the opposed edges of one or both mandibles near the end; as in the shrike, vireo, and 
some wrens, thrushes, and warblers. 4. The conirostral (Lat. conus, a cone), or conical, suffi- 
ciently defined by its name, and illustrated by the great finch family and some allied ones. — 
B, among water birds. 5. The longirostral (Lat. longus, long), or long, an aquatic style of 
the tenuirostral, best exhibited in the great snipe family. 6. The pressirostral (Lat. pressus, 
pressed), or the compact, illustrated by the plovers, etc., and quite likely analogous to the 
conirostral. 7. The cultrirostral (Lat. culter, a knife), cutting, perhaps analogous to the 
dentirostral, exemplified in the heron group. None of these terms are now used to indicate 
natural groups, nor have we such absurdities as the ‘‘ orders” Fissirostres, Tenwirostres, ete. 
A swallow, for instance, and a swift are equally fissirostral, though only distantly related to 
each other; a swift is very closely related to a humming-bird, though the latter is extremely 
tenuirostral ; and birds of contiguous genera may be dentirostral or not. The words are 
nevertheless convenient incidental terms in general descriptions. Various other similar terms, 
expressing special modifications, as lamellirostral (Lat. lamella, a plate), acutirostral (Lat. 
acutus, sharp), ete., are also employed as common names, simply descriptive of 
Other Forms. — A bill is called long, when notably longer than the head proper ; short, 
when notably shorter ; medium, in neither of these conditions. 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 (Lat. teres, cylindric), under neither of these conditions. It is recurved, 
when curved upward ; decurved, when curved downward; bent, when the variation in either 
direction is at an angle; straight, when not out of line with the axis of the head. A bill is 
