VULTURID^E.] OSTEOLOGIA AVIUM. [PoLYBORINjE. 



Subfam. 2. Polyborin^e. 



Polyborus, Vieill. 



Tharus, Mol. 

 Type of Polyborinse. 



Cranium not so long or so much flattened in proportion to its width as in Vulturinoe ; 

 a central depression continued only to the vertex. Lacrymal bones triangular, and only 

 continued about halfway over the orbital process of the frontal bone, similar to those of 

 Sarcoramphus. Orbital septum with a large irregular posterior perforation. Occipital 

 ridge well marked; protuberance well denned. Foramen magnum round, not quite 

 horizontal. Atlar tubercle small, rounded. Nasal orifices oval, much inclined down- 

 wards. Palatine bones very broad posteriorly and much narrowed anteriorly, with a 

 nearly central elevated and dependent ridge. Interarticular bones short, and similar in 

 form to Sarcoramphus. 



Vertebrae somewhat lengthened ; processes short. 



Sternum convex, very slightly narrowed anteriorly; lower edge of the keel much 

 rounded ; anterior part very slightly receding, the edge curved inwards considerably to 

 the manubrial process, which is long and flattened perpendicularly ; muscular ridge for 

 the attachment of the pectoralis minor well defined ; posterior margin of the sternum 

 with a slight indentation on each side of the keel not well defined. 



Bones of the pelvis weak in comparison with those of Vulturinw ; the ilium projecting 

 far over the ischium ; the foramina as in Sarcoramphus. 



Coracoids long ; axillary foramen and channel well marked. 



Fureulum strong, flattened, indented at the junction of the rami instead of prolonged 

 into a process, as in Sarcoramphus. 



Scapula and wing-bones similar to those of Sarcoramphus, but of less power. 



Femur with the trochanter slightly developed ; the distal extremity much enlarged. 



Tibia similar to Sarcoramphus. 



Fibula two-thirds the length of the tibia, and anchylosed for its proximal third to the 

 tibia, and again so at its tip. 



Measurements. 



Tenths. 



Length of humerus 43 



Length of ulna 44^- 



Length of radius 43| 



Length of metacarpus 25 



Length of femur .31 



Length of tibia 46 



Length of metatarsus 42 



Length of sternum 33 



Illustration. 

 Sternum, Plate I. fig. 9. 



23 



Tenths. 

 Breadth of posterior margin of sternum 20 



Breadth of anterior margin of sternum 16 



Depth of keel 8 



Length of head . . 32 



Breadth of head 17 



Length of pelvis 38 



Breadth of pelvis I ...... 17 \ 



