180". 1 PROF. HUXLEY ON THE CLASSIFICATION OF BIRDS. 463 



The posterior face of the proximal end of the tarso-mctatarsus 

 presents two ridges (of which tlie inner is very much stronger and 

 more prominent than the ahnost obsolete outer) separated by a deep 

 and wide groove. 



The skull is broad, and the bones of the brain-case have a spongy 

 diploij. Basipterygoid processes are always present, and the tumid 

 and spongy maxillo-palatines are separated by an interval, which 

 may be wide throughout, or reduced to a cleft below. 



The peculiarly spongy lachrymal remains distinct for a long time, 

 if not throughout life, from the frontal bones and the prefrontal 

 processes. 



The external nares may be long, but are never pervious, the 

 septum being well ossified. 



The sternum is commonly four-notched, and has a manubrial 

 process. 



The proximal ends of the clavicles are comparatively little ex- 

 panded or recurved, and become very slender towards their sym- 

 physis. The clavicular process of the corsicoid fits 'nto an excava- 

 tion on the outer surface of the clavicle. The scapular process of 

 the coracoid is prolonged forwards to meet the clavicle. The lower 

 larynx possesses one pair of intrinsic muscles. 



■f- The CathartidcB comprise the Vultures of the New World (Ca- 

 thartes and SarcoraDiphus) *. The feathers have no aftershaft, and 

 the oil-gland wants the circlet of feathers. The phalanges of the 

 hallux, taken together, are about half as long as those of the outer toe, 

 and the articular surtace of its short metatarsal lies above the level 

 of the articular faces of the other metatarsals ; the claws are bluut 

 and comparatively straight, and the fourth toe is not reversible. 



The second and third phalanges of the fourth toe, taken together, 

 are as long as, or longer than, the basal phalanx. 



The basal phalanx of the third toe is longer than either the second 

 or the penultimate, the two latter being subequal. 



The tarso-metatarsus is thick, and its inner edge rounded and not 

 much thinner than the other. 



The posterior face of the proximal end of the bone presents a 

 broad and prominent process, with a truncated posterior surface. 

 This surface has the contour of a heart with its apex downwards, 

 and is divided by a low longitudinal ridge into two slightly excavated 

 surfaces, of which the outer is the smaller. Below, the process 

 passes into a ridge, which runs down upon the middle metatarsal. 



The skull is provided with basipterygoid processes, and has an 

 elongated rostrum. The valley between the lamellar maxillo-pala- 

 tines is both deep and wide. 



The lachrymal bones are so completely anchylosed with the frontals 

 and with the broad prefrontal })rocesses, that all traces of their pri- 

 mitive distinctness are completely lost. 



* I have examined skeletons of Catharlex /ceteris, C. aura, and C. calif ornianus, 

 of Sarcorhainphus gryphus and 5. papa, and compared them with species of Neo- 

 phron, Vultur, Gyps, Gypohierax, and Gypaetun. 



