SKELETON OF PHOKOEHACOS INFLATTJS. 79 



marked by an intermuscular ridge running obliquely downward and inward from the 

 outer edge of the trochanter : in its lower third it forks, one branch running to the 

 upper anterior angle of each of the condyles ; in its upper portion this line no doubt 

 separated the surfaces for the crurceus and the vastus externus. 



There is a deep popliteal fossa, which is separated by a prominent bar of bone from 

 the intercondylar fossa, which is marked by two deep pits for ligaments. 



The outer condyle projects considerably below the inner ; its fibular ridge is very 

 prominent, and the surface for the fibula slightly concave from side to side. On the 

 lower end of the outer condyle is a very distinct facet for the tendon of the outer head 

 of the tibialis anticus. Anteriorly the condyles project considerably, and the rotular 

 channel is comparatively deep. 



Comparing the femur of 1) iomedea with the fossil, we find that it differs, among other 

 points, in the shallowness and form of its popliteal fossa and in the great antero-lateral 

 compression of the lower end of the shaft. The head, moreover, is much less distinctly 

 pedunculate. 



The femur of Grus differs in the somewhat more curved shaft, the elevation of the 

 trochanter above the head, the somewhat shallower popliteal fossa, and the smaller 

 degree of obliquity of the distal articulation. 



In Psophia the trochanter is high and the popliteal fossa shallower than in the fossil. 

 In Cariama the shaft is rather curved and the trochanter is somewhat raised above 

 the head, which is very similar to that of the fossil : the distal end differs only in the 

 somewhat greater shallowness of the popliteal fossa. 



In the Rails the shaft of the femur is always much curved, and the trochanter rises 

 considerably above the head. 



In the Birds of Prey (including Serpentarius) the femur is pneumatic, the trochanter 



rises above the head, and the neck, as a rule, is very short. 



The dimensions of the femur are : — 



mm. 



Length 227 



Width at proximal end 59 



„ at distal end 62 



„ of middle of shaft 25 



Circumference of middle of shaft 81 



The Tibio-tarsus. (Plate XVII. figs. 9 & 10.) 



The tibio-tarsus is a comparatively long and slender bone. The shaft is somewhat 

 flattened on its anterior and posterior surfaces, and tapers slightly towards its distal end. 

 It is straight, but the median border near its distal end curves slightly inward, so 

 that the inner condyle projects considerably inward ; the outer condyle is in a line with 

 the outer border of the shaft. The anterior surface is bordered internally by a strongly- 

 marked linea aspera, which is continuous above with the procnemial crest, and towards 



vol. xv. — part in. No. 4. — October, 1899. N 



