70 Transactions. — Zoology. 



The shaft at one-third of its total length above its distal end is- nearly 

 round in a transverse section, a feature it has in comuion with Circus, 

 whereas the shaft of Aquila is more subelliptic. 



The articular head forms a more distinct tuberosity than in Aquila, which 

 is also observable in Circles ; a broad groove dividing it from the ulnar crest, 

 which advances considerably over the pneumatic foi'amen. 



The radical crest being partly bi'oken off, its whole extent cannot be 

 ascertained. The ridge forming the boundary of the large depression for the 

 iijsertion of the pectoralis major is well marked. 



The articular convexities of the distal extremity ai^e also of considerable 

 size, and well carved out ; the pits for the attachment of the muscles are large 

 and deep, all tending to prove that Harpagornis possessed considerable power 



of flight. 



Ulna. 



Harpagornis moorei. 



This bone has the following dimensions : — 



Inches. 

 Total length ... ... ... ... ... 10-06 



Circumference at its proximal end ... ... ... 3*15 



Circumference at its distal end ... ., ... 2*52 



Circumference of shaft where thinnest ... ... 1'77 



In comparing its total length with the corresponding bone in Aqtiila 



audax, as given in the table of measurements, it will be seen that it is only 



0"68 inch longer, but that it is distinguished from it by its considerable 



thickness and the greater expansion of both articular ends. This is most 



conspicuous when examining the proximal surface, but, considering the great 



breadth of the distal end of the humerus, quite a natural consequence. 



The anconal side of the shaft is rather flatter than in Aquila, so that the 



bone does not exhibit quite such a great curve as the latter. 



The quill knobs are obliterated. 



Harpagornis assimilis. PI. VIII., Figs. 3 and 4. 



Indies. 

 Total length ... ... ... . ... ... 9-35 



Circumference of proximal end ... ... ... 3*00 



Circumference of distal end ... ... ... 2-32 



Circumference of shaft whei-e thinnest ... ... 1*48 



The pachydermal chai'acter of the genus under consideration, when 

 compared with Aquila audax, is well exhibited in this ulna, because, being 

 actually shorter than the corresponding bone in. the Australian sjiecies, it is 

 much shorter in all its proportions. 



The ulna of this species being better preserved than that of Harpagornis 

 moorei has been figured by preference. The two rows of quill knobs, and 



I 



