Lucas oh the Os Promhieiis. 



8' 



ensis, B. virgitiiajiiis^ Scofs brasilianjis, S. asio^ Nyctca scan- 

 diaca, JVitiox albigularc^ Asio otiis, Syrnhnn nebulosuin^ and 

 6\ urale/ise. It is not ^^resent in Sirix Jlammea or 6". perlata^ 

 and should it prove to be present in other genera of the Buboni- 

 dcc than those noted above, it may serve as an additional, though 

 trivial, point of distinction between the families Btcbonidcv and 

 Stris-idcc. 



Left wing of Bidyo viigiiiiaiuis, from below (reduced one third), 

 radius; ii, ulna; c, cuneiform; s, scapho-lunar ; osp, osprominens; 

 epa, tendon of extensor patagii longus. 



The accompanying cut, drawn from a fresh specimen of B . 

 virgniiaiius^ explains the form and position of the os prominens. 



It will be noticed that it is situated on the anterior surface of 

 the distal end of the radius, and runs almost parallel with that 

 bone, instead of standing erect as in the Balconidce. The radial 

 portion of the tensor patagii longus terminates in the os promi- 

 nens, and is not continued to the first metacarpal. 



Apart from the- Owls above noted, this bone has been found in 

 Otogyps calviis^ Hctcrospizias meridioualis^ Buteo melano- 

 IciicHS^ B. peiiiisylvaiiicus^ B. lineatus^ Circus gould/\ Ast?i- 

 rina pucheratn^ and Haliivctiis albicilla. 



A. Os prominens of Otogyps calviis, full size. 



B. " " " Bubo virginianiis, seen from above to show 



articulation with radius, full size. 



