464 PROF. HUXLEY ON THE CLASSIFICATION OF BIRDS. [Apr. 1 I, 



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 pro- 

 cess ; 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 re- 

 curved ; 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 iu 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 Aetomorphse. 



No lower larynx is developed. 



The group of the Gypaetidce contains the Old World Vultures and 

 the other " Raptores diurnxE," except Gijpoyeranus. 



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 i)ha- 

 lanx, 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 ])osterior 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 inter- 

 vening valley. 



The lachrymals commonly remain long distinct (especially in the 

 Vultures). 



The nasal apertures are usually little elongated, and are imi)er- 

 vious by reason of the ossification of the septum. 



The slernum has a more or less distinctly marked manubrial pro- 

 cess. 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 j)roduced to the clavicle. 

 * E. (J. in the Falcons proper and in Polyhorus. 



