EXTERNAL FARTS OF BIRDS. ^ THE BILL. 101 



Four Classes, reprtsonting as many ways in which the two mandibles close upon eacli 

 other at the eml. 1. The epifjnatlwiis (Gr. (Vi, epi, upcjn, yvaBos, gnatlios, 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 hijpognatkom (Gr. vtro, hnpo, under), in which the lower 

 mandible is longer than the other. 3. The paragnathous ((.4r. jrapa, para, at or by), in whicli 

 both are of about equal length, and neither is evidently bent over the other. 4. Themetagna- 

 thotis (Gr. fifTti, 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 e.\(.'niplified, respectively, 

 by the skimmer and the cross-bill (genera Rliynchopa and Loxia). The first is conmion, 

 occurring throughout the birds of prey, the piaiTOts, aud among the jietrels, gulls, etc., etc. 

 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 homy sheath, which often, as among fly- 

 catchers, etc., 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 hjur 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 classitieation, even 

 for the establishment of orders ; but which the progress of the science has shfjwn 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 liirds. 1. The fisnirostral (Lat. /s.shs, 

 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, whippoonvill. 2. The 

 temiirostral (Lat. temtis, slender], or slender, in which the bill is small, kjvg, and with a short 

 cleft; as in the humming-bird, creejier, nuthatch. 3. The dentirostral (Lat. dens, a tocjth), 

 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 alUed ones. — 

 B, among water birds. 5. The longirostral (Lat. longus, long), or long, an acp.iatic style of 

 the tenuirostral, best exhibited in the great snipe family. 6. The pressirostral (Lat. pjressus, 

 pj'essed), or the compact, Illustrated by the plovers, etc., and quite likely analogous to thi' 

 conirostral. 7. The ctdtrirostral (Lat. miter, 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'' Fissiro.'^tres, Tenuirostres, etc. 

 A swallow, for instance, and a swift are equally flssirostral, though only distantly related to 

 each other ; a swift is very closely related to a humming-bird, though the latter is extremdy 

 tenuirostral ; and birds of contiguous genera may be dentirostral or not. The words are 

 nevertheless convenient incidental tenns in general descriptions. Various other similar terms, 

 expressing special modifications, as lamellirostral (Lat. lamella, a plate), aattirostral (Lat. 

 acutus, sharp), etc., are also employed as common names, simply descriptive of 



Other Forms. — A bill is called long, when notably longer than the head prcjper ; .short, 

 when notably slnjrter ; 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. feres, cyliudric), 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 (jf the head. A bill is 



