| OCR Text |
Show 462 PKOF. HUXLEY ON THE CLASSIFICATION OF BIRDS. [Apr. 1 I, divided by the structure of the skull, described above, into two groups -the one containing the Pelicans, the other the remaining genera. 5. The AETOMORPH^E. The rostrum is more or less arched and hooked at the tip, and at its base there is a cere in which the nostrils are pierced. Basipterygoid processes may be present or absent. The maxillo-palatine processes may be concavo-convex lamellae, or may be spongy and fill up the base of the rostrum, but they are always united with an ossification of the septum. The breadth of the articular surface at the distal end of the quadrate bone is greater than its length, the outer condyle extending about as far downwards as the inner. The angle of the mandible is never recurved. The sternum is broad, and has a strong carina. Its posterior edge may be entire, or may have one or two notches on each side. The pelvis and the tarso-metatarsus vary greatly. The feet always possess a hallux ; the fourth toe is never permanently turned backwards, and the anterior toes are never completely or even largely webbed. In other respects they vary. There are always two carotids. The inferior larynx may be wanting, and when developed has not more than one pair of intrinsic muscles. The circlet of feathers may be present or absent upon the oil-gland ; and the contour feathers have, or have not, an aftershaft. The division of the Aetomorphae is equivalent to the " Raptores" of Cuvier-an eminently natural assemblage, and yet one the members of which, as the preceding enumeration of their characters shows, vary in most important particulars. They appear to m e to fall naturally into four well-defined primary groups-the Strigidce, the Cathartidee, the Gypaetidce, and the Gypogeranidce. But this arrangement is so different from that ordinarily adopted, that I shall proceed to justify it by enumerating the principal circumstances in which the members of the several divisions agree with one another and differ from the rest. In the Strigidce, or Owls, the feathers want the aftershaft, and the oil-gland is not surmounted by a circlet of feathers. The hallux is more than half as long as the fourth toe, and on a level with the other toes. The claws are long, curved, and acute, and the fourth toe is reversible. The first three phalanges of this toe are subequal and very short; all three together are not so long as the penultimate phalanx. The basal phalanx of the third toe is not longer than the second, and is far shorter than the penultimate. The tarso-metatarsus is extremely flattened, with strono- lateral ridges, the inner edge being particularly thin ; and, usually,&there is an osseous loop for the extensor tendons on its front face. |
