Note 140 — Chapter II · THE ANATOMY OF A BIRD.[138]

These plates may become united with one another in the middle line, and the birds that possess this arrangement have been called Desmognathæ (δεσμός, “a bond;” γνάθος, “jaw”); or they may be separated by a more or less narrow cleft, in which case the birds in which this is found are called Schizognathæ (σχίζω, “I cleave”). As a matter of fact, the term Schizognathous is confined to those birds in which the above-mentioned vomer is pointed in front, while where it is truncated the birds are called Ægithognathæ (αἴγιθος, “a sparrow,” as the character is seen in these birds). In these groups, however, the Ostriches, or running birds, which are distinguished by having no keel to their sternum, are not included; nor in them is the vomer narrow behind. This broad character of the hinder end of the vomer is seen also in one group of birds with a keeled sternum—the Tinamous—which are consequently distinguished from other “Carinate” birds by the term Dromæognathæ (Dromæus, the Emu).