1911] 



Miller: 



Eagle Tarsi from Eancho La Brea. 



313 



character appears when the proximal articular surface is viewed. 

 The inner hypotarsal ridge shows much the greater development 

 in Geranoa'etus. 



Upon these grounds the three fossil species of long shanked 

 eagles are referred to the two existing genera, Morphnus and 

 Geranoa'etus. 



Morphnus woodwardi appears to have been a rather weak- 

 footed form, as indicated by the slender shaft, small trochleae, 

 weak hypotarsal ridges, small supratendinal loop, and high posi- 

 tion of the papilla of the tibialis anticus. The same indications 

 of weakness are to be seen in the long shanked Geranoa'etus 

 melanoleucus, a species reported to feed upon offal. The mechan- 

 ical advantage sacrificed by thus attaching the tibialis anticus so 

 high up the shaft must be quite appreciable. The shortening of 

 the power arm in the lever of flexion of the foot would, other 

 factors being equal, diminish the lifting power of this segment 

 of the limb. 



In several species of falconids at hand, the relation of the 

 power arm as indicated by the position of the papilla of the 

 tibialis anticus, to the total length of the shaft, has been calcu- 

 lated and is recorded in the table below. 





Resistance 



Power 







arm 



arm 



Ratio 



Thrasaetus harpya (east) 



117.1 mm. 



32. mm. 



27.3% 



Aquila chrysaetos 



100.2 



30.3 



30.2 



Haliaetus leucocephalus alascanus 



97.7 



23. 



23.5 



Archibutio ferrugineus 



89. 



21. 



23.5 



Buteo borealis 



85.5 



17.1 



20. 



Falco peregrinus 



57.5 



11. 



19.1 



Geranoaetus melanoleucus 



114. 



21. 



18.4 



Morphnus guianensis (east) 



103.9 



17.1 



17.1 



Morphnus woodwardi 



129.1 



21.5 



16.6 



Otogyps calvus 



in. .3 



18. 



16.1 



In the collection of the Los Angeles High School, there is a 

 specimen of the tarsometatarsus of this species. The specimen 

 was placed in the author's hands by the instructor of zoology 

 at that institution, Mr. J. Z. Gilbert, for examination. This 

 specimen measures 137.2 mm. in total length, thus exceeding by 

 eight millimeters the type specimen. In the details of its con- 

 tours it corresponds perfectly with the type specimen. 



