NOTES ON THE STRUCTURE OF BIRDS. 
whole osteology of Polyborus , indeed, comes so near that of the 
vultures, that I have some doubts whether that genus ought not 
to be arranged with them instead of with the hawks. There is, 
however, a resemblance to the hawks in the form of the posterior 
margin, in the central or entosternal portion not being prolonged 
beyond the hyposternal or lateral portions, or, in other words, 
beyond the general line of the posterior margin. In all the vul- 
tures I have examined this is the case, distinguishing their skele- 
tons at once from that of the other Raptores. On this account, 
therefore, I shall for the present exclude the Polyborina from the 
true Vulturidce. 
Having now pointed out my reasons for including Serpentanus 
among the Vulturidce , I shall endeavour to show, in a tabular form, 
how that family may be arranged by the forms of the posterior 
margin of the sternum only : — 
VULTURIDCE. 
The Entosternal portion not prolonged backwards beyond the Hyposter- 
nal portion: — 
Keel not prolonged 
to the posterior margin 
of the Entosternal por- 
tion 
f Gypaetinje 
| Gypaetos 
| CaTHARTINA2 . . . 
{ 
| Cathartes 
I Neophroninas . . . 
Neophron 
^ Gy pokier ax (?) 
f Lateral orifices large — 
■j Hyposternal portion slightly 
( elongated laterally. 
f Lateral orifices of mode- 
rate size — Hyposternal por- 
tion much elongated. 
f Lateral orifices small — 
j Hyposternal portion not 
[ elongated. 
Keel prolonged to 
the posterior margin 
of the sternum 
f Serpentarinas 
| Serpentarius . . . 
f Without lateral orifices— 
•j Entosternal portion much 
[ elongated. 
VuLTURINAS. 
Vultur .... 
Gyps 
Otogyps .... 
With lateral orifices — 
Entosternal portion very 
slightly elongated. 
133-4 
Sa RCORAMPHINA3 
l Barcoramphvs 
Without lateral orifices— 
Entosternal portion very 
slightly elongated. 
