1867.] PROF. HUXLEY ON THE CLASSIFICATION OF BIRDS. 465 



The inferior larynx is present, and has one pair of intrinsic 

 muscles. 



-f- The division of the Gypogeranida consists of the single genus 

 Gypogeranus, whicli, though allied to the Falcons in some respects, 

 is so peculiar in others that it must he regarded as the type of a 

 family apart. The feathers have an aftershaft, and the oil-gland a 

 circlet (Nitzsch). The phalanges of the elevated hallux, taken to- 

 gether, are not more than half as long as those of the outer toe. 



The basal phalanx of the fourth toe is much longer than the distal, 

 and longer than the second and third together. These are subequal 

 and very short, shorter than the fourth phalanx. 



The basal phalanx of the third toe is much longer than the second, 

 and the second is slightly longer than the third. 



The shaft of the long tarso-metatarsal bone is prismatic, its antero- 

 posterior diameter being as great as, or greater than, the transverse. 

 The upper part of its posterior face presents a prominent process 

 terminated by an expanded cordate surface, somewhat as in the Ca- 

 thartidce. 



The skull has basipterygoid processes, and the spongy maxillo- 

 palatines are completely united, so as to obliterate the intermediate 

 valley. The lachrymal remains distinct ; and the long external nares 

 may be pervious, or not, according to the extent of the ossification 

 of the septum. The sternum is escutcheon-shaped, and elongated. 

 The posterior edge is convex, with two small emarginations on each 

 side. There is a distinct manubrial process. 



The proximal ends of the clavicles are not expanded, and are 

 hardly excavated. A great median process extends from the sym- 

 physis of the clavicles, and becomes anchylosed with the sternum. 

 The scapular process of the coracoid is not prolonged to meet the 

 clavicle. 



In the pelvis nothing is to be seen of that bending of the post- 

 acetabular region of the ilium downwards and forwards, which is so 

 strongly marked in most of the other Aetomorphse. 



- 6. The PsiTTACOMORPH^. 



The rostrum is arched and hooked at the extremity, and is regu- 

 larly articulated with the frontal region of the skull. 



Basipterygoid processes are wanting. 



The palatines are vertically elongated posteriorly, while anteriorly 

 they are horizontally flattened and moveably united with the rostrum. 

 The maxillo-palatines are spongy. The lachrymal and the post- 

 orbital bend towards one another and frequently unite below the 

 orbit. 



The orbital process of the quadrate bone is very small ; and its 

 distal end presents only one facet (which is compressed from side to 

 side and convex from before backwards) for the mandible. The rami 

 of the latter are deep, and pass into one another by a rounded trun- 

 cated symphysis. 



Proc. Zool. Soc— 1867, No. XXX. 



