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Show 464 PROF. HUXLEY ON THE CLASSIFICATION OF BIRDS. [Apr. 1 1, The external nares are extremely long and are pervious, the septal ossification not extending between them. The sternum has, at most, a mere rudiment of the manubrial process ; and its posterior margin exhibits either four slight excavations, or two holes externally and two notches internally. The proximal ends of the clavicles are greatly expanded and recurved ; and their outer sides present a deep and wide excavation, at the bottom of which lies the pneumatic foramen. A great part of this excavated surface is left uncovered in front of the clavicular process of the coracoid when the bones are articulated together. The scapular process of the coracoid is not prolonged forwards to meet the clavicles. The posterior or ischio-iliac edge of the os innominatum presents a deep notch, which is not found in the other Aetomorphae. No lower larynx is developed. The group of the Gypaetidee contains the Old World Vultures and the other " Raptores diurnee," except Gypogeranus. With the single exception of Pandion (according to Nitzsch) their contour feathers have aftershafts. The oil-gland is provided with a circlet of feathers. The phalanges of the hallux, taken together, are much more than half as long as those of the fourth toe ; and the articular surface of the metatarsal descends to the level of the other or nearly so. The second and third phalanges of the fourth toe, taken together, may be longer or shorter than the basal; but the basal phalanx is always much longer than the second. The basal phalanx of the third toe is longer than the second phalanx, which is sometimes (less commonly) longer, sometimes (more commonly) shorter than the penultimate phalanx. The tarso-metatarsus is greatly flattened, and its inner edge thin and produced. On the upper part of its posterior face are two ridges (of which the inner is the more prominent) separated by a deep and wide groove. There are no basipterygoid processes. The maxillo-palatines are more or less spongy ; and narrow, or completely obliterate, the intervening valley. The lachrymals commonly remain long distinct (especially in the Vultures). The nasal apertures are usually little elongated, and are impervious by reason of the ossification of the septum. The sternum has a more or less distinctly marked manubrial process. The posterior margin may be entire, and has not more than two holes or notches. The proximal ends of the strong clavicles are expanded, recurved, and deeply excavated externally; but the large clavicular process of the coracoid fills the whole of the anterior moiety of this excavated surface when the bones are articulated. The scapular process of the coracoid sometimes is* and sometimes is not produced to the clavicle. * E. g. in the Falcons proper and in Polyborus. |