Elements of comparative zoology (1904) Elements of comparative zoology elementsofcompar1904king Year: 1904 354 SYSTEMATIC ZOOLOGY. flying birds possesses a strong ridge or keel (carina) below, to which the muscles of flight are attached. In some flightless birds the keel is lacking. The skull is noticeable from the great extent of the fusion of the separate bones; for the single condyle for articulation with the neck and for the suspension of the lower jaw by means of a movable quadrate bone, as in the lizards, snakes, etc. The shoulder-girdle consists of scapula, coracoid, and clavicles, the
Elements of comparative zoology (1904) Elements of comparative zoology elementsofcompar1904king Year: 1904 354 SYSTEMATIC ZOOLOGY. flying birds possesses a strong ridge or keel (carina) below, to which the muscles of flight are attached. In some flightless birds the keel is lacking. The skull is noticeable from the great extent of the fusion of the separate bones; for the single condyle for articulation with the neck and for the suspension of the lower jaw by means of a movable quadrate bone, as in the lizards, snakes, etc. The shoulder-girdle consists of scapula, coracoid, and clavicles, the latter noticeable for their union into a V-- shaped 'wish-bone' or furcula. In the wing the reduction in bones of the wrist and hand is remarkable. The bones of the wrist are all united into two, while the three fingers FIG. 149.—Skull of quail, g, quadrate bone. which remain have few joints and are partly united. In the hind limb the fibula is short, but especially noticeable is the great lengthening of two of the ankle-bones, the result being that the heel is elevated some distance from the ground. Birds are grouped in three divisions or subclasses, Saururse, Odontornithes, and Ornithurse, the first two of which are extinct; the third contains the ten thousand known species of living forms.
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