24 DIFrERENT KINDS OF BILLS. 



vertebrate animals. All bills, thus similarly constituted, have been 

 divided* into 



§ 45. FoDR Classes, representing as many ways in which the two man- 

 dibles close upon each other at the end. 1. The ejrujnathous (Gr. ejpi, upon, 

 ijnathoH, 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 hijpognathous (Gr. hypo, under), in which the lower mandible is 

 longer than the other. 3. The paragncUhoits (Gr. para, at or by), in which 

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

 4. The melarjnathous (Gr. meta, with, beside, etc.), in which the points of 

 the mandibles cross each other. The second and fourth of these are ex- 

 tremely rare ; they are exemplified, respectively, by the skimmer and the 

 cross-bill (genera 295 and 60). The first is common, occurring through- 

 out the birds of prey, the parrots, and among the petrels, gulls, etc., etc. 

 The great majority of birds exhibit the third; and among them, there is 

 such evident gradation into epignatbism, that it is necessaiy to restrict the 

 latter to its complete development, exhibited in the intermaxillary bone di- 

 vested of its horny sheath, which often, as among flycatchers, etc., forms a 

 little overhanging point, but does not constitute epignatbism. These classes, 

 it should be added, though always applicable, and very convenient in de- 

 scriptions, are purely arbitrary, that is, they by no means correspond to 

 any four primary 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 



§ 46. Other Classes, for many years used as a large basis for ornitho- 

 logical classification ; 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 : — Jv, among laud 

 bii'ds. 1. The Jissirostral, or cleft, in which the bill is small, short, and 

 Avith a very large gap running down the side of the head, as in the swallow, 

 chimney-swift, whippoorwill. 2. The tenidrostral, or slender, in which the 

 Ijill is small, long, and with a short cleft; as in the humming-bird, creeper, 

 nuthatch. 3. The dentirostral, or toothed, in which, with a. various gen- 

 eral 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, or conical, suffi- 

 ciently defined ))y its name, and illustrated by the great finch familj^ and 

 some allied ones. B, among water birds. 5. The longirostral, or long, an 

 aquatic style of the tenuirostral, best exhibited in the great snipe family. 6. 

 The pressirostral, or the compact, illustrated by the plovers, etc., and quite 

 likely analogous to the conirostral. 7. The cullrirostral, cutting, perhaps 

 analogous to the dentirostral, exemplified in the heron group. None of 

 these are now used to express natural groups, in strict definitions; all are 



* By the writer : Proc. Aoail. Nat. Sci. Phila., Dec. 18l«), [i. 213. 



