. Handbook of field and general ornithology; a manual of the structure and classification of birds . tal processes and forl<ed manu- . ,, , . briiim; five ribs reaching sternum, stcmum IS generally greatly coiivcx irom one rib floating. ^j^^ ^^ ^j^^^^ ,^^^ ^j^^^^^ • ^^ ^^^^^ ^^j^^^ ^j^j^j^ have prominent pleurostea, produced in angular costal processes. Thisborder is also thickened, and presents on each side a well-marked,smooth-faced groove, in which the expanded feet of the coracoid bonesare instepped and firmly articulated. These deep grooves commonlymeet in the middle ; are occasionally
. Handbook of field and general ornithology; a manual of the structure and classification of birds . tal processes and forl<ed manu- . ,, , . briiim; five ribs reaching sternum, stcmum IS generally greatly coiivcx irom one rib floating. ^j^^ ^^ ^j^^^^ ,^^^ ^j^^^^^ • ^^ ^^^^^ ^^j^^^ ^j^j^j^ have prominent pleurostea, produced in angular costal processes. Thisborder is also thickened, and presents on each side a well-marked,smooth-faced groove, in which the expanded feet of the coracoid bonesare instepped and firmly articulated. These deep grooves commonlymeet in the middle ; are occasionally continuous from one side tothe other; sometimes each crosses to the other side a little costal processes on each side also have thickened edges, witha series of articular facets for the ribs, Avhich gives this border afluted or serrate profile. Generally the fore half, or rather less, ofthe side border of the sternum is thus articular; and it is only suchcostiferous (rib-bearing) extent of sternum which corresponds to thewhole body of the bone in a mammal, all the rest being ANA TOMY OF BIRDS 215 The singular carinate sternum of Notornis, and the ratite bone ofApteryx, are concave crosswise along the front border, and bear thecoracoids far apart, at the summits of antero-lateral projections. A sternum is generally concavo-convex in every direction,bellying downward; somewhat rectangular, it may be long andnarrow, or short, broad, and squarish. It is commonly longer thanbroad, with convex front border, a median beak, which is oftenforked, jDrominent antero-lateral corners, pinched-in sides (bulgingin tinamou) and indeterminate hind border. The keel usuallydrops down lowest in front, sloping or curving gently up to thegeneral level behind, with a concave (rarely protuberant) verticalborder, and j)ronounced apex, to which the clavicles may or maynot be ankylosed, as they are in a pelican, for instance. In Opis-thocomus the clavicles ankylose with the manubriu
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Keywords: ., bookauthorcouesell, bookcentury1800, bookdecade1890, bookyear1890
